By Guy Faulconbridge and Lidia Kelly
MOSCOW (Reuters) -Ukraine pummelled two Russian regions with drones on Tuesday as its ground forces tried to smash through defensive lines in a bid to carve out even more territory in its biggest attack on Russian territory since the war began.
Ukrainian soldiers crossed the Russian border, about 530 km (330 miles) southwest of Moscow, a week ago, in a surprise attack that President Vladimir Putin said was aimed at improving Kyiv's negotiating position ahead of possible talks and slowing the advance of Russian forces along the rest of the front.
Russia's defence ministry said its air defence units destroyed 12 drones over the Kursk region, one over the Belgorod region and one over Voronezh. Russian officials in Kursk and Belgorod put out warnings of missile attacks.
Russia and Ukraine have given vastly different estimates of the area of Russian territory under Ukrainian control, with Kyiv claiming 1,000 square kilometres (386 square miles) but Russian officials saying the area was less than half that.
Russian war bloggers reported intense battles across the Kursk front as Ukrainian forces tried to expand their control near Lgov, Bolshoy Soldatskoye and Korenevo - though they said Russia was bringing in both soldiers and heavy weaponry and repelled some of the Ukrainian attacks.
The fate of the town of Sudzha, through which Russia pumps gas from Western Siberia through Ukraine and on to Slovakia and other European Union countries, was unclear. Gazprom (MCX:GAZP) said on Monday it was still pumping.
Some Russian war bloggers and Ukrainian Telegram channels said the town was in the control of Ukraine, though Reuters was unable to independently verify the battlefield accounts and Russia has yet to give details on the situation in Sudzha.
About 14.65 billion cubic metres (bcm) of gas was supplied via Sudzha in 2023 - about half of Russian natural gas exports to Europe, or about 5% of EU consumption.
The Ukrainian attack has underscored how effective small highly-mobile units can be against the vastly numerically superior Russian army, though by dedicating forces to Kursk, Ukraine could weaken other parts of the front.
Russia on Monday reported that it was gaining in other parts of the front, though Moscow has had to move reserves to halt the Ukrainian advance.
President Volodymyr Zelenskiy told Ukrainians in his nightly address that the operation was a matter of Ukrainian security and the Kursk region had been used by Russia to launch many strikes against Ukraine.
"Russia must be forced to make peace if Putin wants to fight so badly," Zelenskiy said.
Russia invaded Ukraine in February 2022 and now controls 18% of Ukrainian territory. Until the surprise attack on Russia, Ukraine had been losing territory to Russian forces despite hundreds of billions of dollars in U.S. and European support aimed at stopping and even reversing the Russian advance.
In Kursk, 121,000 people had already left or have been evacuated and another 59,000 were in the process of being evacuated, local officials said. In Russia's Belgorod region, which borders Kursk, 11,000 civilians were also evacuated, the region's governor said.
Ukraine's air force said on Tuesday that Russia launched 38 attack drones and two ballistic missiles on Ukraine overnight. The whole country was briefly under air raid alerts early on Tuesday, but these have since been called off.