Ukrainian authorities said yesterday they had closed three checkpoints on the border with Russia after nightly assaults by separatists.

The move came as the government vowed to beef up its security presence to counter pro-Russian rebels, amid reports of continued fighting in the country’s east.

The three checkpoints, all in the volatile Lugansk region, were targeted in attacks by pro-Russian rebels overnight Wednesday to yesterday, the border guards said in a statement.

"After an exchange of fire, the threat to the lives of people crossing the border prompted the evacuation of civilians and border guards at the checkpoints."

The statement added that Chervonopartyzansk, Dolzhansky and Chervona Mogyla checkpoints had been temporarily closed, and that the Russian side had been notified. Insurgents fighting for an independent "People's Republic" remain in control of large parts of eastern Ukraine, and officials reported continued sporadic small arms fire yesterday.

Donetsk, home to about one million people, has been reduced to a state of near-anarchy following heavy fighting between Ukrainian forces and pro-Russian rebels around its international airport.

The fighting has left about 40 dead according to reports, and the airport will remain closed at least until the end of the month, as the security of flights cannot be guaranteed.

The streets of Donetsk are nearly deserted and under the control of insurgents, who man numerous checkpoints in the area. Ukrainian forces, who launched an "anti-terrorist operation" nearly two months ago, intensified their activities on Tuesday, concentrating their efforts on the rebel stronghold of Slavyansk, more than 100 kilometres north of Donetsk.

Two Ukrainian soldiers have lost their lives in this week's fighting, while numerous insurgents have been killed,