* Residents: soldiers extorted people before clashes erupted
* Militants blow up pipeline after repair, two soldiers dead (Adds two more soldiers killed in separate incident)
SANAA, April 8 (Reuters) - Seven people were killed in clashes between army deserters and tribesmen in south Yemen on Monday, officials and residents said, in another sign of disorder in a country of multiple conflicts next to oil export giant Saudi Arabia.
Restoring security in Yemen is a priority for the United States and its Gulf allies to contain threats from al Qaeda militants and separatist tribes to Saudi Arabia and nearby sea lanes where oil tankers pass.
In a separate incident, two Yemeni government soldiers were killed and two were wounded in a gunfight with tribesmen who had blown up the main Maarib oil pipeline in south Yemen only two weeks after it was repaired, the Interior Ministry and a military source said.
Local officials in the city of Redaa and residents reported the clash between deserters and tribesmen in the southern province of al-Bayda.
"Dozens of former members of the Republican Guard left their camp and entered Redaa with their weapons and cars," one resident said.
"They deserted their base and started extorting people before they eventually assaulted a resident," he said, prompting tribesmen to intervene to try and stop them.
A local government official said the soldiers had been demanding additional financial benefits which they said the government had promised them for fighting battles against al Qaeda militants in al-Bayda.
He said four soldiers and three armed tribesmen were killed in the clashes.
In December, President Abd-Rabbu Mansour Hadi ordered an overhaul of the military to try and unify ranks split between allies and foes of his predecessor, Ali Abdullah Saleh, who was ousted last year by mass protests but remains influential.
Hadi's overhaul entails restructuring the armed forces into four major units and abolishing the Republican Guard, an elite force headed by Brigadier General Ahmed Saleh, the former president's son and one of Hadi's adversaries.
A U.N. Security Council monthly forecast report published on March 28 was sceptical of Hadi's ability to bring the armed forces under one umbrella.
"While Hadi issued presidential decrees in December 2012 aiming to centralise the armed forces, many agree that he has yet to unify and maintain them under his control," it said.
An Interior Ministry official said Obeida tribesmen had blown up the Maarib pipeline that brings crude oil from the Safer field to Ras Isa port on the Red Sea.
A local military source said the tribesmen ambushed an army force sent to escort repair crews sent to fix the pipeline. "Two soldiers were martyred and two were injured in the ambush," the source told Reuters.
A protracted closure of the line during an anti-Saleh uprising in 2011 forced Yemen's biggest refinery at Aden, the main southern port, to close, leaving the country dependent on fuel donations from Saudi Arabia and imports.
Yemen's oil and gas pipelines have been repeatedly sabotaged by Islamist militants and disgruntled tribesmen since anti-Saleh protests created a power vacuum. Fuel shortages resulted and export earnings vital to impoverished Yemen plunged.
(Reporting by Mohammed Ghobari; Writing by Mahmoud Habboush; Editing by Yara Bayoumy and Michael Roddy)