KYIV, Ukraine (AP) — Russian President Vladimir Putin claimed victory in the battle for Mariupol on Thursday, even as he ordered his troops not to take the risk of storming the giant steel plant where the last Ukrainian defenders in the city were holed up.

Instead, he directed his forces to seal off the Azovstal plant “so that not even a fly comes through.”

After nearly two lethal months of bombardment that have largely reduced Mariupol to a smoking ruin, Russian forces appear to control the rest of the strategic southern city, including its vital but now badly damaged port. But the Ukrainian troops have stubbornly held out.

Putin’s comments came as satellite images showed more than 200 new graves in a town where Ukrainian officials say the Russians have been burying Mariupol residents killed in the fighting. The imagery, from Maxar Technologies, shows long rows of graves stretching away from an existing cemetery in the town of Manhush, some 20 kilometers (12 miles) from Mariupol.

A few thousand defenders, by Russia’s estimate, have been holed up for weeks along with hundreds of civilians in the sprawling steel plant, as Putin’s forces pounded the site and repeatedly demanded they surrender.

But on Thursday, the Russian leader declared victory without taking the plant, which covers 11 square kilometers (4 square miles) and is threaded with some 24 kilometers (15 miles) of tunnels and bunkers.

“The completion of combat work to liberate Mariupol is a success,” he said in an appearance with his defense minister. “Congratulations.”

Instead of mounting a frontal attack on the plant, Russia apparently intends to maintain the siege and wait for the defenders to surrender when they run out of food or ammunition.

Ukraine scoffed at the notion of a Russian victory.

“This situation means the following: They cannot physically capture Azovstal. They have understood this. They suffered huge losses there,” said Oleksiy Arestovich, an adviser to Ukrainian President Volodymyr Zelenskyy.

The capture of Mariupol would represent the Kremlin’s biggest victory yet of the war in Ukraine. It would help Moscow secure more of the coastline, complete a land bridge between Russia and the Crimean Peninsula, which Russia seized in 2014, and free up more forces to join the larger battle now underway for Ukraine’s eastern industrial heartland, known as the Donbas.

“The Russian agenda now is not to capture these really difficult places where the Ukrainians can hold out in the urban centers, but to try and capture territory and also to encircle the Ukrainian forces and declare a huge victory,” retired British Rear Adm. Chris Parry said.

As for the drive in the east, the Russians continued heavy air and artillery attacks but did not appear to gain any significant ground over the past few days, according to military analysts, who said Moscow’s forces were still gearing up for a heavier offensive.

A senior U.S. defense official, speaking on condition of anonymity to discuss the Pentagon’s assessment, said the Ukrainians were hindering the Russian effort to push south from Izyum.

Rockets struck a neighborhood of Kharkiv on Thursday, and at least two civilians were burned to death in their car. A school and a residential building were also hit, and firefighters tried to put out a blaze and search for anyone trapped.

Western nations, meanwhile, rushed to pour heavy weapons into Ukraine to help it counter the offensive in the east.

U.S. President Joe Biden announced an additional $800 million in military assistance for Kyiv, including heavy artillery, 144,000 rounds of ammunition and drones.

But he also warned that the $13.6 billion approved last month by the U.S. Congress for military and humanitarian aid is “almost exhausted” and more will be needed.

Russia Defense Minister Sergei Shoigu estimated 2,000 Ukrainian troops remained at the steel plant. Ukrainian officials said about 1,000 civilians were also trapped there along with 500 wounded soldiers. Shoigu said the site was blocked off and predicted it could be taken in days.

“I consider the proposed storming of the industrial area pointless,” Putin responded, saying he was concerned about Russian soldiers.

“There is no need to climb into these catacombs and crawl underground through these industrial facilities,” the Russian leader added. “Block off this industrial area so that not even a fly comes through.”

All told, more than 100,000 people were believed trapped with little or no food, water, heat or medicine in Mariupol, which had a prewar population of about 430,000.

The city has seized worldwide attention as the scene of some of the worst suffering of the war, including deadly airstrikes on a maternity hospital and a theater.

Ukraine has repeatedly accused Russia of launching attacks to block civilian evacuations from the city. On Thursday, at least two Russian attacks hit the city of Zaporizhzhia, a way station for people fleeing Mariupol, though no one was wounded, the regional governor said.

For weeks now, Russian officials have said capturing the mostly Russian-speaking Donbas is the war’s main goal. Moscow’s forces opened the new phase of the war this week along a 300-mile (480-kilometer) front from the northeastern city of Kharkiv to the Azov Sea.

“They’ve realized if they get sort of held up in these sort of really sticky areas like Mariupol, they’re not going to cover the rest of the ground,” Parry said.

Britain’s Defense Ministry said that Russia probably wants to demonstrate significant successes ahead of Victory Day on May 9, the proudest day on the Russian calendar, marking the defeat of Nazi Germany in World War II.

“This could affect how quickly and forcefully they attempt to conduct operations in the run-up to this date,” the ministry said.