Russia battles Ukrainian troops for a third day after major incursion

Russian forces were battling Ukrainian troops for a third day after they smashed through the Russian border in the Kursk region, an audacious attack on the world's biggest nuclear power that has forced Moscow to call in reserves.

In one of the biggest Ukrainian attacks on Russia of the two-year war, around 1,000 Ukrainian troops rammed through the Russian border in the early hours of August 6 with tanks and armoured vehicles, covered in the air by swarms of drones and pounding artillery, according to Russian officials.

Ukrainian forces swept through the fields and forests of the border towards the north of the border town of Sudzha, the last operational trans-shipping point for Russian natural gas to Europe via Ukraine.

President Vladimir Putin cast the attack as a "major provocation". The White House said the United States - Ukraine's biggest backer - had no prior knowledge of the attack and would seek more details from Kyiv.

Russia's most senior general, chief of general staff, Valery Gerasimov, told Putin on Wednesday that the Ukrainian offensive had been halted in the border area.

But multiple pro-Russian military bloggers said the battles continued into Thursday and that civilians were being evacuated.

"Sudzha is basically lost to us. And this is an important logistics hub," said Yuri Podolyaka, a popular Ukrainian-born pro-Russian military blogger, adding that Ukrainian forces were pushing north towards Lgov.

"In general, the situation is difficult and continues to deteriorate, despite the fact that the pace of the Ukrainian offensive has noticeably dropped."

The Ukrainian army has remained silent on the Kursk offensive. Some Russian bloggers criticised the state of border defence in the Kursk region, saying that it had been far too easy for Ukrainian forces to slice through them.