As attacks by Ukrainian-aligned insurgents in Russian territory stretched into a third day on Wednesday, concerns were rising in Russia that the rare border incursion could create new battlefield problems — and it has increased calls for the military to expend more resources defending against such assaults.

A group composed of anti-Kremlin Russian fighters, the Free Russia Legion, claimed responsibility for the attack that began on Monday, which has produced the most intense fighting on Russian territory since the war began.

The Russian defence ministry said on Tuesday that the attackers had been pushed back across the border into Ukraine. But the violence in the Russian border region, Belgorod, continued overnight, with “a large number of attacks” by drones and an attack that damaged a gas pipeline and caused a small fire, according to the regional governor, Vyacheslav Gladkov.

“The night was not entirely calm,” Gladkov wrote on Telegram on Wednesday morning, adding that houses, cars and office buildings in the city of Belgorod and other settlements had been damaged.

The Kremlin’s spokesman, Dmitri S. Peskov, said on Tuesday that Moscow was “deeply concerned” about the attack while using the violence to try to further justify Russia’s invasion of Ukraine.

The Security Council did meet after a shorter outbreak of violence on the border in Bryansk in March when soldiers led by the same group briefly took control of a Russian village before being pushed back into Ukraine.

But some ardently pro-Russian voices openly expressed fear that the attacks in Belgorod would create new battlefield challenges for Russia, whose only significant military victory in the past nine months came in the last few days.

New York Times News Service