Armed militants believed to be holding over 350 pupils and adults hostage in a school in southern Russia have released 26 women and children.

Details of the release, which took place Thursday night, have yet to be disclosed.

Russian government authorities' efforts to open a channel of negotiations are continuously being hampered as the hostage-takers are refusing the delivery of food and water to the school in the town of Beslan, located near the border with war-torn Chechnya.

The militants, presumed to Chechens, have called for the withdrawal of Russian troops from Chechen territory and for the release of incarcerated comrades.

Russia's ITAR-Tass News Agency quoted the attackers as saying earlier on Wednesday that they would kill 50 hostages if one of their own is killed and 20 hostages if one of their number is injured.

According to law enforcement officials, nine adults, including one of the militants, were killed and four injured as a result of the initial hostage-taking attack, in which scores of children aged between six to 17 are being held captive.

Earlier on Wednesday, at least 17 insurgents wearing belts laden with explosives seized the hostages just hours after a suicide bomber killed at least ten and injured dozens outside a busy Moscow subway station. A group that said it had downed two planes in Russia last week, killing nearly 90, has claimed responsibility for the hostage taking.