SANAA, July 19: Yemeni government forces shelled a southern town overrun by radical Islamists, killing at least 20 militants in the past two days, residents said on Tuesday.

In the capital Sanaa, meanwhile, Yemen's disparate opposition groups announced a new alliance they say will unite all forces seeking to oust longtime President Ali Abdullah Saleh.

Saleh, who is in Saudi Arabia for treatment of wounds from a June attack on his palace, remains in power despite more than five months of mass protests across Yemen calling for his ouster.

The uprising against his 33-year rule has led to a collapse in security across the country, the Arab world's poorest and home to an active Al Qaeda branch, and the US fears Al Qaeda-linked groups could exploit the chaos.

Since the uprising began in mid-February, radical Islamists have seized entire towns in southern Abyan province, and government troops have been fighting to dislodge them. Over the weekend, Yemeni army forces began shelling the militant- controlled town of Jaar in Abyan. —AP