A Ukrainian military helicopter has been shot down by pro-Russian rebels over the eastern city of Slavyansk, killing 14 troops.

Among the dead was an army general, according to authorities in the capital Kiev.

Slavyansk has been at the centre of fighting between insurgents and government forces in recent weeks.

Authorities in the capital Kiev have condemned the unrest which it blames on Moscow.

But this is rejected by Russia which claims to have no influence over the militants, who argue they are protecting the Russian-speaking population in the east of the country.

Meanwhile a rebel leader in Slovyansk said his fighters are holding four observers from the Organisation for Security and Cooperation in Europe (OSCE), but indicated they would be released shortly.

The OSCE said one of its four-man monitoring teams had gone missing in Donetsk on Monday.

Rebels have previously kidnapped military observers from the OSCE.