Ukraine struck Russia's Kursk region with drones and rockets on Wednesday as part of what Russian officials said was a major attempt to smash through the Russian border and force Russian generals to scramble troops from other parts of the front.
Ukraine struck back on Tuesday.
Ukrainian forces unleashed a major attack by land and air to penetrate Russia near the border town of Sudzha, 530 km (330 miles) southwest of Moscow, the defence ministry and other Russian officials said. It is the last operational trans-shipping point for Russian gas exports to Europe via Ukraine.
The officials said Russia repelled the attacks - one of the largest incursions into Russia since the war began in 2022 - but there were signs of major military movements in the area. Russia sent reserves to help shore up Russian defences.
Ukraine has not commented on the events.
Alexei Smirnov, the acting governor of the Kursk region, said there had been rocket and drone attacks overnight, and told civilians to take cover away from windows
"Due to the situation in the border areas of the region, medical institutions are replenishing the supply of donated blood," Smirnov said, adding that there would be a mobile blood donation point set up in Kursk.
The battles around Sudzha come at a crucial juncture in the war: Ukraine is losing territory and Kyiv is deeply concerned that U.S. support could drop off if Donald Trump wins the November election in the United States.
Trump has said he would end the war, so both Russia and Ukraine are keen to gain the strongest possible bargaining position on the battlefield while pinning down Russian forces and showing the West that it can still mount major battles.
Shoigu said on Tuesday that the window for peace was narrowing and that the longer it took for Kyiv to begin to talk about terms, the costlier the peace would be for the Ukrainian people.
BATTLE OF KURSK
Russian military bloggers reported intense battles in the border area, including around the village of Sverdlikovo, and said Ukraine was concentrating forces near the border.
"The fighting will be fierce," said Yuri Podolyaka, an influential Ukrainian born pro-Russian military blogger. "It's definitely not going to end quickly."
"Even if the enemy fails to break through (and no one will give guarantees for now), there will be artillery attacks and drone attacks. And in large numbers," said Podolyaka.
Ukraine's attack on Russia's Kursk border region has targeted the civilian population, Russia's foreign ministry said.
"This is another terrorist act," Maria Zakharova, the foreign ministry spokesperson, told Russian radio broadcaster Sputnik, according to Russia's RIA state news agency. "It is obviously directed against a peaceful population, against a civilian population."
Both Kyiv and Moscow say their attacks do not target civilians though civilian losses in the war have been vast.
Officials said the border town of Sudzha had come under assault and Smirnov said a Ukrainian attack drone had hit an ambulance outside the town, killing the driver and a paramedic and wounding a doctor.
A senior Orthodox clergyman said Ukrainian shelling had set ablaze a cathedral and other buildings within a large monastery outside Sudzha, but no one was hurt.
Forces describing themselves as voluntary paramilitaries fighting on Ukraine's side penetrated parts of Belgorod and Kursk region this year, triggering a major push by Russian troops to carve out a buffer zone in Ukraine's northeast.
