Russia calls in reserves after shock Ukraine incursion

Russian forces were battling Ukrainian troops for a third day on Thursday 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 in the two-year-old 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.

The incursion has come as a shock to Russia, nearly two-and-a-half years since President Vladimir Putin sent his army into Ukraine in February 2022. Putin has cast the Ukrainian offensive as a "major provocation". The White House denied any prior knowledge of the attack. Heavy fighting was reported near the town of Sudzha, where Russian natural gas flows into Ukraine, raising concerns about a possible sudden stop to transit flows to Europe. Kursk's regional acting governor, Alexei Smirnov, said that thousands of residents had been evacuated.

Russia's defence ministry said that the army and the Federal Security Service (FSB) had halted the Ukrainian advance and were battling Ukrainian units in the Kursk region. Some Russian bloggers said Ukraine's forces were pushing towards the Kursk nuclear power station, 60 kms northeast of Sudzha.

"Units of the Northern group of forces, together with the FSB of Russia, continue to destroy armed formations of the Armed Forces of Ukraine in the Sudzhensky and Korenevsky districts of the Kursk region, directly adjacent to the Russian-Ukrainian border," the Russian defence ministry said.