President Vladimir V. Putin ordered Russian forces on Thursday not to storm a steel plant where Ukrainian troops were holding out in Mariupol, but to blockade it completely.

The Russian leader, who called a direct assault “impractical”, also tried to claim victory in the besieged city even as Russian forces have been unable to subdue the remaining Ukrainians, who have given no indication they were ready to surrender.

Putin’s comments on national television were an effort to assert control of a strategic city that Russia has failed to fully capture despite two months of bombardment that has killed tens of thousands of civilians, according to Ukrainian officials. Mariupol’s mayor called for a ceasefire on Thursday to allow more civilians who remain trapped in the city to flee, a day after four buses carrying evacuees managed to leave, according to Ukraine’s deputy Prime Minister.

It was not clear if any evacuation corridors would apply to the hundreds of civilians believed to be sheltering in bunkers along with Ukrainian soldiers under the Azovstal steel plant. Putin commanded his troops to ensure that “not even a fly” could pass through the blockade of the site.

In his nightly address, President Volodymyr Zelensky of Ukraine repeated his pleas for international allies to send “serious and heavy” arms. Russia expanded its assault across eastern Ukraine, adding more weaponry as its forces made minor territorial gains along the 300mile front, military analysts said.

On Wednesday, Putin took the provocative step of testlaunching a new intercontinental ballistic missile, declaring it a warning that western nations should “think twice” before they “try to threaten our country”. The test has only added to concerns in the Biden administration that the Russian leader is more isolated than ever as he redoubles his offensive to gain full control of the eastern Ukraine region known as the Donbas.

Ukraine derided Putin’s attempt to avoid a final clash with its forces in the city as an acknowledgment that he lacked the troops to defeat them.

In a televised meeting at the Kremlin, Putin told defence minister Sergei Shoigu: “You successfully completed the combat effort to liberate Mariupol. Let me congratulate you on this occasion, and please convey my congratulations to the troops.”

He added: “I consider the proposed storming of the industrial zone unnecessary. I order you to cancel it ... There’s no need to climb into these catacombs and crawl underground through these industrial facilities ... Block off this industrial area so that not even a fly can get through.”

It falls short of the unambiguous victory Moscow has sought after months of brutal combat in a city reduced to rubble. “They physically cannot take Azovstal, they have understood this, they have taken huge losses there,” Ukrainian presidential adviser Oleksiy Arestovych said.

New York Times News Service and Reuters