Ukraine has the right according to international law to attack legitimate military targets in Russia to defend itself, NATO Secretary General Jens Stoltenberg said during a visit to new alliance member Sweden on Friday.

“Ukraine has the right to self defence,” Stoltenberg told a news conference with Swedish Prime Minister Ulf Kristersson at a military base near Stockholm.

“The right to self defence also includes the right to hit legitimate, military targets on the territory of the attacking party, the aggressor, in this case Russia.”

The Kremlin said this week that Western nations supplying Ukraine with weapons to strike Russian territory will have to reckon with Russia, after President Vladimir Putin said he was considering arming the West’s enemies in retaliation.

“This is a war of attack that Russia has begun against a peaceful, democratic neighbouring country, Ukraine, that at no point has been a threat to Russia,” Stoltenberg said.

“There is no question that Ukraine has the right to hit targets on Russian territory.”

The Russian Defence Ministry on Friday accused Ukrainian forces of firing five U.S.-supplied ATACMS missiles at the Russian-controlled eastern Ukrainian city of Luhansk in an attack it said had wounded 20 people, including children.

Separately, Leonid Pasechnik, the Russia-installed governor of the region, said on the Telegram messenger app that three people had been killed in the strike and that the total number of victims had risen to 35, including three children.

The Defence Ministry said in a statement that its air defence systems had shot down four of the five missiles, but that one of the missiles had damaged two residential apartment blocks, something it alleged was deliberate.

Pasechnik said 33 buildings had been damaged, including two schools and three kindergartens. He said rescuers were continuing to pull people from the rubble.