About 40 fighters escaped from a jail in southern Yemen in the mayhem caused by a bomb blast on Thursday, a local official and southern media said.

State media said six people were injured in the explosion but quoted an Interior Ministry security official as denying the mass escape reports as "rumours spread by certain media".

The local government official said around 40 prisoners escaped after the blast in the southern province of Dalea.

Witnesses and southern media said those who escaped from the police jail belonged to Yemen's southern anti-government movement, which opposes the rule of President Ali Abdullah Saleh.

North and South Yemen united in 1990, but many in the south -- home to most of Yemen's oil industry -- complain northerners have seized resources and discriminate against them.

Elsewhere in Yemen's south, an activist was shot dead and three others were injured when security forces dispersed a protest in the town of Radfan in Lahej province, the local official and media reports said.

Reuters