British Prime Minister Boris Johnson has urged other leaders to join a six-point plan to respond to Russia's invasion of Ukraine, ranging from humanitarian support to inflicting the most economic pain possible on Moscow.
Ahead of meetings with leaders from Canada, the Netherlands and Central Europe in London next week, Mr Johnson said on Saturday that Russian President Vladimir Putin's invasion had to fail and be seen to fail.
"It is not enough to express our support for the rules-based international order - we must defend it against a sustained attempt to rewrite the rules by military force," Mr Johnson said in a statement.
He listed his objectives, which included an international humanitarian coalition for Ukraine, support for its self-defence and maximising economic pressure on Moscow.
Mr Johnson also called for diplomatic paths for de-escalation with the full involvement of Ukraine's government, stronger security in the European-Atlantic area, and an end to the "creeping normalisation" of Russian activities in Ukraine.
After meeting the prime ministers of Canada and the Netherlands on Monday, Mr Johnson is due to host leaders from the Czech Republic, Hungary, Poland and Slovakia - countries experiencing an influx of refugees caused by the invasion - on Tuesday.
Britain is planning to move more quickly to sanction Russian businessmen through new legal measures which will be sent to parliament on Monday.
'The situation is catastrophic and getting worse day by day'
The humanitarian situation in the southern Ukrainian port of Mariupol is "catastrophic" and it is vital that civilians be evacuated, a senior official from Doctors Without Borders (MSF) warned Saturday.
The city, which lies near the border with Russia, has been under siege by Russian forces, and a Saturday ceasefire to allow civilians to leave failed to materialise.
"It is imperative that this humanitarian corridor, which could have been created today but which has not really been put in place following non-respect of the ceasefire, is put in place very quickly to allow the civilian population, women and children, to get out of this city," MSF's emergency coordinator in Ukraine, Laurent Ligozat, told AFP.
"...the situation is catastrophic and getting worse day by day," he added.
The strategic city and Azoz sea port is considered a key one for Russia to capture.
"Today there is no more water; people have huge problems accessing drinking water and this is becoming a crucial issue," said Ms Ligozat.
"There is no more electricity, there is no heating. Food is running out, shops are empty.
"For several days quite simply, there has been nothing coming in or going out of the city."
It came as Ukraine urged the West to ramp up military assistance to the besieged country, including warplanes, as Mr Putin escalated warnings against NATO.
"The highest demand that we have is in fighter jets, attack aircraft, and air-defense systems," Ukrainian Foreign Minister Dmytro Kuleba told a small group of journalists on the Poland-Ukraine border.
"If we lose the skies, there will be much more blood on the ground," he said after a meeting with his United States counterpart, Antony Blinken.
Separately, Ukrainian President Volodymyr Zelenskyy "made a desperate plea for Eastern European countries to provide Russian-made planes" that Ukrainians are trained to fly, US Senate Majority Leader Chuck Schumer said following a video call between legislators and the Ukrainian leader.
As the conflict moved into its 10th day, Mr Putin warned the West of a wider war if a no-fly zone is set up, as his forces resumed an offensive against a key Ukrainian city where security fears stalled a planned evacuation.
While Mr Zelenskyy criticized NATO for ruling out a no-fly zone - amid worries it could spark a wider war - Mr Putin spoke of "colossal and catastrophic consequences not only for Europe but also the whole world" if such a zone were established.
"Any movement in this direction will be considered by us as participation in an armed conflict by that country," Mr Putin said.
An intense round of shuttle diplomacy continued as Israeli Prime Minister Naftali Bennett made a surprise visit to the Kremlin for three hours of talks with Mr Putin, Bennett's office said.
It was Mr Putin's first face-to-face meeting with a foreign leader since the invasion began.
The Israeli leader later spoke with Mr Zelenskyy.
Kyiv had asked Israel - which has strong relations with both Russia and Ukraine - to launch a dialogue with Moscow.
For Mr Zelenskyy, under an escalating bombardment that has flattened more and more infrastructure and sent nearly 1.4 million civilians fleeing, the Western military alliance's "no" to a no-fly zone essentially gave "the green light for further bombing of Ukrainian cities and villages".
The strategic city of Mariupol, on the Azoz Sea, has for days been under attack and without electricity, food and water.
After Russia declared a ceasefire to open a humanitarian corridor, city officials said the population of 450,000 could begin to leave by bus and private cars.
Firefighters try to extinguish a fire at a house in Chernihiv, Ukraine, as Russia's invasion entered its 10th day. Source: Getty / Anadolu Agency
A Russian Defence Ministry spokesman later announced the assault was back on, citing "the unwillingness of the Ukrainian side to ... extend the ceasefire".
The siege came as Russian forces inched closer to the capital, Kyiv, in an assault that has become ever more indiscriminate - and deadly.
Working-class towns such as Bucha and Irpin are in the line of fire, and air raids Friday broke many people's resolve to stay.
"They are bombing residential areas - schools, churches, big buildings, everything," said accountant Natalia Dydenko, glancing back at the destruction she was leaving behind.
Dozens of civilians have been killed in the northern town of Chernihiv. Those remaining live in craters or among ruins.
Scenes of devastation
"There were corpses all over the ground," a man who gave his name only as Sergei told news agency AFP, as air raid sirens wailed. "They were queueing here for the pharmacy that's just there, and they're all dead."
AFP reporters saw scenes of devastation - despite Moscow's insistence it is not targeting civilian areas.
A defiant Mr Zelenskyy on said Saturday that Ukrainian forces were counterattacking around Kharkiv, the country's second largest city, inflicting "such losses on the invaders that they have not seen even in their worst dream".
Kuleba was equally defiant, saying, "Ukraine is bleeding, but Ukraine has not fallen, and stands both feet on the ground."
He added: "The myth of the unbeatable and almighty Russian army is already ruined."
Since Mr Putin's army invaded on 24 February, Russia has pummeled Ukrainian cities, with officials reporting hundreds of civilians killed.
But Moscow has so far seized only two key cities - Berdiansk and Kherson on Ukraine's southern Black Sea coast.
A checkpoint set up at a road heading to the city of Kyiv, Ukraine, Saturday, 5 March, 2022. Source: AAP / Emilio Morenatti/AP
The Kremlin said it was waiting for a third round of talks with Ukraine in Belarus.
The new talks would take place Monday, the Ukrainian side said.
The war has had serious global economic impacts, and the IMF warned on Saturday that its effects would be "all the more devastating" should the conflict escalate.
Russia's business and other contacts with the West have been steadily cut. Moscow has suspended all flights by flagship carrier Aeroflot, effective Tuesday.
And the list of major companies suspending operations in Russia has grown steadily, now including Spanish clothing giant Zara and fashion chain owner Inditex.
In Washington, some lawmakers have urged President Joe Biden to take tougher measures, including banning Russia's oil imports - though the administration is wary of seeing high fuel prices rise further.
With fears growing of direct conflict between NATO and Russia - both nuclear-armed - the US and Moscow have set up a new direct phone line to reduce the risks of "miscalculation", the Pentagon said on Friday.
US General Mark Milley, chairman of the joint chiefs of staff, became the latest Western figure to rule out a no-fly zone, saying it would mean taking on Russian air forces - something, he said in Riga, that neither NATO nor member state leaders are interested in.
