Russian forces have begun using “siege tactics” against a town near the Ukrainian border and just north of Kiev, the Pentagon says, raising the specter of further civilian casualties as the fighting escalates.

A senior defense official told reporters on Sunday that Russian troops appeared to be ‘taking on a siege mentality’ against Chernihiv, surrounding the city and increasing rocket attacks, which the official said was a ‘worrying’ development. .

“When you adopt siege tactics, it increases the likelihood of collateral damage to civilian infrastructure as well as civilian life, as a siege becomes an all-out effort to take a city,” said the official, who spoke on condition of anonymity. discuss events on the ground in Ukraine. The official could not confirm whether the civilians were directly targeted or simply became collateral damage as Russian forces advanced on various Ukrainian towns.

Russian troops entered Kharkiv overnight, and although they remain about 30 kilometers (19 miles) north of downtown Kiev, reconnaissance elements are operating in the capital, the senior police official said. defense. Some members of these reconnaissance units wore Ukrainian uniforms and were unmasked by locals, the official added. According to the Pentagon’s assessment on Sunday morning, the Russian army has still not taken control of any Ukrainian city.

The Pentagon estimates that Russian forces are still about 50 kilometers (31 miles) from the center of Mariupol, a major port city along Ukraine’s southeast coast. “Mariupol will be defended,” said the senior defense official, who credited Ukraine with mounting a “creative resistance” that was both “heroic” and “inspiring”. But the official warned that Russia still had significant “operational advantages” over Ukraine and would likely learn from the mistakes that had slowed the advance of Russian forces in the days to come.

The Russians faced logistical challenges in maintaining support for units operating in Ukraine, the senior defense official noted. The Pentagon has also determined that some, but not the majority, of the more than 320 missile launches Russia has undertaken against Ukraine have failed.

Russia has already put about two-thirds of the combat force it amassed around Ukraine into the country, according to the official – who warned that the remaining third of its force that Moscow had not yet committed in combat always represents “a lot of Combat Power.”

Meanwhile, the Ukrainians retained the ability to use their air and missile defenses against Russia, but Kyiv’s assets were downgraded, the official said.