MOSCOW: Ukraine's border guard service said a number of its servicemen were injured in an insurgent attack on their camp in eastern Ukraine.

The officials said in a statement Monday that some 100 armed insurgents attacked the border guards' camp in Luhansk, a major eastern Ukrainian city not far from the Russian border, in the early hours.

Border guards responded with fire on the attackers whose numbers swelled to 400 a few hours later.

The fighting was still ongoing, the border guard service said.

The conflict between Ukrainian government forces and pro-Russian insurgents in eastern Ukraine escalated markedly in the last week, with rebels' attempting to seize a major airport Monday and the shooting down of a Ukrainian military helicopter.