ADEN/SANAA - A bomb killed nine people in southern Yemen on Wednesday, a local official said, and tribal sources in the north said 15 more died in sectarian clashes.

Yemen has been buffeted by violence mainly involving militants from al Qaeda in the south and Shia tribesmen and rival Islamists in the north since mass protests in 2011 forced long-serving President Ali Abdullah Saleh to step down. The country is also battling a secessionist movement in the south and the nationwide spread of an al Qaeda insurgency.

In the southern town of Saber in the Lahej province, a local official said suspected al Qaeda militants detonated a roadside explosive charge as bomb squads tried to defuse it while residents looked on, killing a total of nine people and wounding another 14.

The official said three bomb disposal experts, two local residents and four members of security forces died in the explosion, which al Qaeda had claimed.

In north-eastern Yemen, tribal sources said the fighting between the Shia Houthi fighters and rivals loyal to the Islamist Islah party erupted in al-Jouf province on Tuesday night with both sides using heavy weaponry including tanks that were previously captured from the army.

Ceasefire agreements reached with government intervention have repeatedly failed to stop the conflict between the two sides. At least 200 people were killed and more than 35,000 displaced last month when Houthi rebels overtook Amran, 50 kms (30 miles) north of the capital Sanaa.

The Houthis, named after their leader's tribe, have said their fight was against rivals loyal to the Islamist Islah party - which has links to the Muslim Brotherhood - rather than the government.

The Houthis, who control much of the northern Saada province bordering Saudi Arabia and next to al-Jouf, are trying to consolidate their power in the north as the country moves towards a federal system that gives more power to regional authorities.

US-allied Yemen, an impoverished country of 25 million that shares a long border with the world's top oil exporter Saudi Arabia, has been in turmoil since 2011 when mass protests forced the veteran president, Ali Abdullah Saleh, to step down.