Ukraine on brink of major breakthrough as another Russian region at risk of invasion
Fierce battles are said to have broken out, with Russia's military deploying heavy artillery and fighter jets.
Russian media reports claim Ukraine has attempted to launch a new invasion of its territory on August 27.
Some 500 Ukrainian troops supported by armoured fighting vehicles reportedly launched attacks on border checkpoints in the Belgorod region.
Roughly 200 soldiers tried to cross the border at Nekhoteyevka and another 300 at Shebekino, according to the Mash telegram channel.
Fierce battles are said to have broken out, with Russia's military deploying heavy artillery and fighter jets.
One Russian source told the Shot channel: "The Armed Forces of Ukraine approached the border with the Belgorod region in eight armoured vehicles - the battle with Russian border guards is taking place near Nekhoteyevka.
"When approaching the border, they were driven back by artillery and aircraft, but those who had taken refuge in the forest belt continued to fire. They hit the checkpoint."
Belgorod's governor appeared to confirm that an attack was underway in a statement on his Telegram channel.
Vyacheslav Gladkov said: “Information has appeared that the enemy is trying to break through the border of the Belgorod region.
"According to the Russian Ministry of Defence, the situation at the border remains difficult, but controllable. Our military is carrying out planned work.”
Don't miss...
Russian missile strikes hotel in centre of Ukraine 'filled with civilians' [LATEST]
British soldier killed in Russian missile strike pictured for first time [NEWS]
Satellite pics show 100s of Russian facilities in range of US-supplied missiles [LATEST]
Ukraine stunned Putin's army after launching a surprise incursion into the Kursk region on August 6.
Kyiv's army claims it now controls almost 500 square miles of enemy territory and around 93 settlements.
Last week, President Volodymyr Zelensky said Ukraine's army was still advancing, although the pace of its progress had slowed down.
There have been signs of the fighting spilling over from the Kursk region into neighbouring Belgorod.
A unit of the Ukrainian 252nd Battalion appeared to have entered the village of Poroz on August 10.
Russia also claimed that Ukraine unsuccessfully attacked the Kolotilovka border checkpoint on August 12.
Overnight on Monday, Vladimir Putin's army launched more aerial attacks on Ukraine, killing at least four people.
