Yemeni troops, tanks advance on al Qaeda-held town

ADEN/SANAA (Reuters) - Hundreds of Yemeni troops backed by tanks advanced in a bid to retake a coastal town from al Qaeda-linked fighters on Monday, residents said, part of a U.S.-backed offensive in a country Washington sees as a frontline against Islamist militants.

"They are getting ready to fight," one resident, who declined to be named, told Reuters by telephone. Via text message, the head of the southern military zone asked people living in the area not to use the roads around Shaqra and two other towns controlled by militants.

Shaqra lies on Yemen's southern coast, along a major shipping route that is also the gateway for Somalis entering the country to fight alongside militants.

The United States and its Gulf allies are alarmed by deteriorating security in Yemen, where al Qaeda-linked militants gained a foothold during a popular uprising against former President Ali Abdullah Saleh.

While Saleh grappled with the protests that eventually toppled him, militants went on a rampage in the southern province of Abyan, gunning down officials, looting ammunition depots, and for the first time in history, seizing territory.

The United States, which helped engineer Saleh's replacement by his deputy in February, is backing the offensive in the south and has stepped up its campaign of drone strike assassinations of alleged al Qaeda members who it says plot attacks from Yemen.

It has also sent dozens of military trainers and stepped up aid to Yemen where it wants President Abd-Rabbu Mansour Hadi to reunify the military and focus on driving militants from their strongholds in Abyan.

Yemeni troops have moved into the centre of Zinjibar, capital of Abyan province, where they fought militants on Sunday. They also clashed with Islamist fighters near the town of Jaar, some 30 km (20 miles) to the north.

"LIKE A PLAGUE"

Meanwhile, two suicide bombers targeting an army checkpoint in Lawdar, another town in Abyan, killed four people and wounded another, said the Defence Ministry. The bombers, one of whom was dressed as a woman, were also killed.

"The attack was targeting Colonel Mohammed Batreeh, the head of military intelligence in Abyan province," a local official told Reuters. "He survived, but the innocent people were the ones who got killed."

A third suicide bomber struck in the same place later on, blowing himself up when volunteer pro-government fighters told him to surrender.

Militants retreated last month from the town of Lawdar, also in Abyan, after encountering stiff resistance from fighters who have arranged themselves into popular committees to defend their land.

"Getting rid of those (Islamist fighters) needs time. They are like a plague," said Abu Saada, a tribesman fighting alongside the army in Abyan.

While fighting raged in the south, at least 34 people were killed in clashes overnight between Sunni Muslim Salafis and Houthi Shi'ite rebels in northern Yemen.

The Houthis have exploited political upheaval in Yemen to carve out their own state within a state in the rugged northern province of Saada, on the border with Sunni-ruled Saudi Arabia, the world's top oil exporter.

Saudi Arabia, wary of the rising regional power of Shi'ite Iran and grappling with its own Shi'ite unrest in eastern provinces, fought the Houthis in northern Yemen in 2009.

The U.S. envoy to Yemen said earlier this year there were signs that Shi'ite Iran was becoming more active in the country, posing a threat to its security and stability. Iran denies interfering in Yemen.

Saudi Arabia, a major regional U.S. ally, says Iran is fomenting unrest among its own Shi'ites in its eastern provinces and in neighbouring Sunni-led Bahrain.

A spokesman for the Salafis - who see Shi'ites as heretics and espouse a puritanical creed with many followers in Saudi Arabia - said Houthi fighters attacked them on Sunday night in the Kataf area of the northern Saada province.

"We have regained control of a mountain site in the al-Damaj area after heavy clashes with the Houthis during which 18 of the attackers were killed along with 16 of ours," the spokesman told Reuters on Monday. Dozens were wounded in the clashes, he said.

(Reporting by Mohammed Ghobari in Sanaa and Mohammed Mukhashaf in Aden; Writing by Rania El Gamal; Editing by Jon Hemming and Ralph Gowling)