* Residents flee clashes in Haradheere

* Al Shabaab militants halt work by foreign NGOs

* Mortar barrages kill 13 in capital Mogadishu

* Rebel leader Aweys vows to fight on

(Adds 13 dead in Mogadishu fighting, paragraph 9-10)

By Abdi Sheikh and Abdi Guled

MOGADISHU, Aug 8 (Reuters) - Gun battles between clan militiamen killed at least 17 people and wounded 30 on Saturday at a pirate stronghold on the coast of Somalia, witnesses said.

The fighting began overnight and intensified in the morning, forcing most of Haradheere's residents to flee, local man Farah Aden told Reuters by satellite telephone.

"The two clans are fighting over land and a girl who was raped in the forest. Unfortunately, the battles spread into town ... Fighting is going on fiercely," he said.

Somalia has been torn by civil war since 1991, and the government of President Sheikh Sharif Ahmed controls only small pockets of the rubble-strewn capital Mogadishu.

Pirates who attack vessels using the shipping lanes linking Europe to Asia through the Gulf of Aden operate from several remote coastal bases including Haradheere.

One pirate in the lawless central Somali port said he was worried the bloodshed would cut the sea gangs' profits.

"We are all members of these two clans, and we are worried that this fight might end up being taken out on to the ocean," the pirate, who gave his name as Mohamed, told Reuters by satellite phone from Haradheere.

Violence in Somalia has killed more than 18,000 people since the start of 2007 and uprooted another 1 million. Western security agencies say the failed Horn of Africa state is a haven for extremists plotting attacks in the region and beyond.

HUMANITARIAN WORK HALTED

In the latest violence in Mogadishu, mortar bombs killed 13 people and wounded 36 others on Saturday.

"I believe there will be more casualties. Many shells dropped on different places," said ambulance official Ali Muse.

President Ahmed's forces are battling hardline Islamist rebels including the al Shabaab group, which Washington accuses of being al Qaeda's proxy in Somalia.

Al Shabaab halted the work of four foreign aid agencies on Saturday, saying they were cooperating with U.N. relief organisations already expelled from areas under its control.

Sheikh Aynanshe Hussein, an al Shabaab commander in the southern town of Jamame, named the four as U.S. charity Mercy Corps, Italy's Cooperazione Internazionale, Briton's Oxfam and UK-based international relief group Muslim Aid.

A local Somali partner organisation, the Jubba Foundation, was also told to suspend its activities.

"These agencies turned deaf ears to our warnings and continued illegal acts," Hussein told Reuters by telephone.

Residents said al Shabaab fighters had taken over the groups' compounds in Jamame, about 60km (37 miles) north of Kismayu. One local aid worker said the gunmen were looting valuables from the charities' offices. Hussein denied this.

REBEL LEADER "TO FIGHT ON"

Last month, al Shabaab banned the U.N. Development Programme, U.N. Political Office for Somalia and U.N. Department of Safety and Security from operating in its territory.

In a sign of international support for the Somali government, U.S. Secretary of State Hillary Clinton held talks with Ahmed in neighbouring Kenya on Thursday and pledged more aid for his administration.

Sheikh Hassan Dahir Aweys, the prominent leader of another insurgent group, Hizbul Islam, issued a statement in Mogadishu on Saturday condemning U.S. policy.

"We thought the Obama administration would positively change Somalia's politics, but it has worsened," Aweys said.

"America wants to colonise all the world's governments, particularly Muslim countries, to loot their natural resources. We shall continue fighting until we reach our goal." (Additional reporting by Sahra Abdi in Nairobi and Mohamed Ahmed in Mogadishu; Writing by Daniel Wallis; Editing by Robert Woodward)

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