Hundreds of Afghan security forces have surrounded a notorious high-security jail where an uprising by up to 2,000 prisoners is under way.
Taleban and al-Qaeda members as well as ordinary criminals are involved.
Sources have told the BBC that seven people have been killed during the rioting, although top Afghan officials have denied any deaths.
Scores of security forces continued to arrive at Kabul's Pul-e-Charkhi jail as negotiation attempts apparently failed. (. . .)
Our correspondent said gunshots could still be heard from within the prison walls.
Trouble apparently started at about 2200 (1730 GMT) on Saturday in Block 2 - which houses 1,300 inmates - after a change in prison uniform rules.
By Sunday evening local time, up to 750 inmates jailed for ordinary criminal offences in another block had begun burning furniture in support of the Block 2 prisoners.
Some reports said the riot developed into an escape attempt, with prisoners trying to get over the walls.
Negotiation attempts? Since when do we negotiate with terrorists. Oh yeah, since the Iran-Contra deal.