The evacuation of people from the besieged south-eastern Ukrainian port city of Mariupol was halted on Saturday because Russian forces were not abiding by a deal to pause hostilities, local officials said.
"For security reasons, the evacuation is therefore postponed," Mariupol city authorities said on Telegram, adding that negotiations continued with Russia on how to "ensure a safe humanitarian corridor."
"We ask all residents of Mariupol to return to their places of refuge," it pleaded.
A ceasefire had been announced early Saturday - the tenth day of Russia's offensive - which would have allowed inhabitants of Mariupol and nearby Volnovakha, a much smaller city, to leave via agreed upon exit routes.
Russia and its allies in Ukraine blamed Kiev for putting the ceasefire in jeopardy.
The Defence Ministry in Moscow said the agreed-upon humanitarian corridor had been shelled and pointed the finger at Ukrainians. It said shots were also fired at Russian troops' positions from Mariupol.
Moscow-backed separatists in the Donetsk region, in which Mariupol and Volnovakha are located, blamed the Kiev government for the continued fighting, saying "Ukrainian nationalists" were planning "provocations."
A strategic city
The implementation of an organized route out of areas that have seen intense fighting in recent days would represent a key step forward in helping imperilled Ukrainians.
Mariupol is a strategic city on the Sea of Azov that has been pounded by Russian artillery for days. It is surrounded.
Mayor Vadym Boichenko has said his city of 440,000 people no longer has water, heat or electricity and is suffering from food shortages.
Despite coming under "relentless" attack for the past five days, Boichenko said Ukrainian troops had not allowed the Russians to enter the city proper.
Before the postponement was announced, Boichenko said buses were ready to carry civilians out, but that they could also leave the city in their own cars along prescribed routes.
Volnovakha, with a population of about 20,000, is located about 65 kilometres north of Mariupol.
The status of Volnovakha evacuation was not clear, nor were there numbers on how many people may have been able to leave Mariupol before the ceasefire broke down there.
In a video address, Ukrainian President Volodymyr Zelensky said women, children and elderly people need to be able to leave the cities while food and medicine must be allowed in.
"All those who need help should be given the opportunity to get out," the president said. "All those who want to defend their town should continue the fight."
Zelensky said his side had done everything possible to ensure the ceasefire held.
The capture of Mariupol and Volnovakha would be a significant win for Moscow, as Russian troops would then begin to be able to join up with their counterparts elsewhere in the Donetsk region and in the Crimean Peninsula.
Moscow had recognized the regions of Luhansk and Donetsk, controlled by pro-Russian separatists, as independent states in February.
Afterwards, the leaderships of the self-proclaimed "Donetsk and Luhansk People's Republics" had called on Russian President Vladimir Putin for help to protect them from the Ukrainian military.
Putin then ordered the start of a "special military operation" on February 24, which led to the invasion of Ukraine from the north, south and east.
On Saturday, Putin warned Western powers against imposing a no-fly zone over Ukraine, an operation that has been demanded by Zelensky but adamantly rejected by NATO and the United States out of fear it would dramatically escalate the war.
"Any movement in this direction will be considered by us as participation of the respective country in an armed conflict," Putin said.
Putin also repeated his demands that, in order for the war to end, Ukraine must demilitarize and become a neutral buffer between Europe and Russia.
In his video message on Saturday, Zelensky said the Russian army had not achieved its objectives, but nearly 10,000 troops had been killed in action. That number could not be independently verified and is far higher than the 498 fatalities acknowledged by Moscow earlier this week.
Efforts to encircle Kiev
The Ukrainian armed forces said Russia continued its efforts to encircle the capital, Kiev, and the second-largest city of Kharkiv, while the attacks were kept up on other cities as well.
Defence Minister Oleksii Reznikov wrote on Twitter that more than 66,000 Ukrainians had returned home from abroad "to defend their country."
In Russia, flagship airline Aeroflot said it was stopping all international flights as of Tuesday, with the exception of service to Belarus. Russian flights have been in disarray since the European Union, Britain, United States and Canada closed airspace to Russian aircraft.
Putin, meanwhile, said he had no reason to declare martial law in Russia right now, a potential step that has worried many in the country.
Imposing martial law would require external aggression or fighting in specific regions, Putin said in Moscow, according to Russian news agencies. "But we do not have such a situation, and I hope it will not come."