Kyiv, Sep 11 (IANS): Ukraine's military says its forces have retaken over 3,000 sq km (1,158 sq miles) during a rapid counter-offensive in eastern Ukraine, BBC reported.

The remarkable advance, if confirmed, means Kyiv's forces have tripled their stated gains in little over 48 hours.

On Thursday evening, President Volodymyr Zelensky put the figure at 1,000 sq km, and then 2,000 sq km on Saturday evening.

On Saturday, the eastern counter-attack saw Ukrainian troops enter the vital Russian-held supply towns of Izyum and Kupiansk.

But UK defence officials have warned that fighting has continued outside those towns. And officials in Kyiv said Ukrainian forces were still fighting to gain control of a number of settlements around Izyum, BBC reported.

Russia's Defence Ministry confirmed its forces' retreat from Izyum itself and Kupiansk, which it said would allow its forces "to regroup" in territory held by Moscow-backed separatists.

The Russian ministry also confirmed the withdrawal of troops from a third key town, Balaklyia, in order to "bolster efforts" on the Donetsk front. Ukrainian forces entered the town on Friday.

At the same time, the head of the Russia-installed administration in the Kharkiv region recommended that its people evacuate to Russia "to save lives".

Unverified footage on social media appeared to show long queues of traffic building up at border crossings. The Governor of the Belgorod border region in Russia, Vyacheslav Gladkov, said "thousands" of people had crossed into the country.

Gladkov said on Saturday that mobile catering, heating, and medical assistance would be available to people entering Russia, BBC reported.