Dozens of casualties in Yemen mosque blast

A bomb hidden in a motorcycle exploded outside a mosque in Yemen's volatile northern city of Saada on Friday causing many casualties, a security source said.

The blast happened as worshippers, including Yemeni army officers, were leaving the Salman Mosque after Friday prayers, the source said.

It was not immediately clear how many people were hurt as rescue workers were still helping casualties at the scene.

It was not known who planted the bomb in Saada, but the northwestern region has been rocked by sporadic violence since a conflict broke out in 2004 between government forces and rebels loyal to Abdul-Malik al-Houthi.

Hundreds of people have been killed and thousands have fled their homes in Saada since the conflict began.

Seven Yemeni troops were killed late on Tuesday in an ambush by the rebels, who often clash with troops of the U.S.-allied Yemeni government and tribes loyal to it.

Yemeni officials say the rebels, from the Zaydi sect of Shi'ite Islam, want to return to a form of clerical rule prevalent in the country until the 1960s. The rebels say they are defending their villages against what they call government aggression.

Sunni Muslims form a majority of Yemen's 19 million population, while most of the rest, including Houthi and his supporters, are Zaydis.

Houthi's supporters, who are not believed to be linked to al Qaeda, oppose Yemen's alliances with the United States.