Separately, a Yemeni government official said a US couple, taken hostage by tribesmen were released on Tuesday, a day after they were seized near the capital Sanaa.

A Yemeni news website seen as aligned with the opposition said the strike was carried out by a drone, a weapon that the Yemen military is not believed to have. US forces helping Yemen fight Al-Qaeda have used drones in the past, but a US diplomat declined to say if the United States was involved.

The strike could heighten anti-US sentiment and broaden Al-Qaeda's appeal among some influential Yemeni tribes, threatening efforts to stabilise a country neighboring oil power Saudi Arabia and busy international shipping lanes, analysts said.

The botched bombing of a US airliner on Dec. 25, claimed by Al-Qaeda's Yemen-based wing, spurred Washington to step up security help to President Ali Abdullah Saleh's government, which faces grave challenges apart from militancy.

The Yemeni mediator, who had been trying to persuade members of the global militant group to surrender, was killed instantly in a pre-dawn strike on his car in Yemen's mountainous Maarib province that also killed three other people.

"Jaber Al-Shabwani, the deputy governor of Maarib, was killed with a number of his relatives and travel companions in an air strike targeting the Wadi Obeida area, where Al-Qaeda elements are present," the provincial official said.

"The deputy governor was on a mediation mission to persuade Al-Qaeda elements to hand themselves over to the authorities, but it seems that the air strike missed its target and struck his car, killing him instantly in addition to three companions," he added, declining to be named. Two others were wounded.
 

On Monday, armed tribesmen kidnapped two US tourists near Sanaa and demanded the release of a relative jailed over a land dispute that was before the courts.

"The Americans have arrived at the interior ministry building in Sanaa," a government official told Reuters.

Authorities had set up road blocks and arrested dozens of members of the kidnappers' families to pressure the abductors.

Another official told Reuters that authorities had promised to look into the kidnappers' demand.

The air strike provoked clashes between the army and members of Shabwani's tribe, and the tribesmen attacked the pipeline that ferries crude oil from Maarib, east of the capital Sanaa, to the Red Sea coast, the official said.

Clashes with the mediator's tribe spread from the countryside to Maarib town, where dozens of tribal gunmen opened fire on government buildings, a local official said.

Security officials said angry tribes blocked a main road to Sanaa, stopping trucks carrying cooking gas and petrol.

The United States and Saudi Arabia want Yemen, which is trying to end a conflict with Shiite rebels in the north while separatist sentiment bubbles over in the south, to focus its efforts on fighting Al-Qaeda, seen as a greater global threat.

Yemen declared war on Al-Qaeda after the failed December attack, stepping up air strikes on the group, which has vowed attacks against Western targets in the oil-exporting region.

A statement from a top Yemeni security body expressed sorrow for Shabwani's death and called him a martyr, without saying who carried out the strike or what type of aircraft was used.

A US diplomat would not discuss the attack. Washington backed Sanaa's fight against Al-Qaeda by training Yemeni forces, sharing information and providing equipment, and recognized Al-Qaeda in Yemen was a threat to both countries, he said.

"So we are working together. The Yemeni forces always take the lead in operations carried out in Yemen using some of that support that we have provided for them through training and information sharing," the diplomat said.

Asked directly if the United States was involved in the strike, he said: "If you want operation-specific details you need to contact the Yemeni government."

Yemen and US military targeted Al-Qaeda figures in Yemen, where Osama Bin Laden's father was born, after the September 11, 2001, attacks. A CIA drone fired a missile that killed Al-Qaeda's leader in Yemen in 2002.

The latest strike had likely intended to hit Ayed Al-Shabwani, an Al-Qaeda leader whose farm in Maarib province was the target of a strike in January, the provincial official said. Shabwani is a relative of the mediator who was killed.

Shipping companies said there was no impact on exports from the attack on the pipeline, which ferries crude to the Ras Isa offshore export terminal. Authorities could not immediately reach the affected area.