SANAA: Gunmen shot dead a Saudi diplomat and his Yemeni bodyguard in Yemen's capital Sanaa on Wednesday in an attack a local security source said appeared to be the work of al Qaeda.

The killing, the latest attack on security officials and politicians in the U.S.-allied state, underscores the challenges facing Yemen since an uprising that began last year toppled President Ali Abdullah Saleh.

Attackers in a four-wheel drive vehicle opened fire on a car carrying Whaled al-Enizi, an aide to the Saudi military attache, near his house in a neighbourhood of Sanaa, a Yemeni security official said. The diplomat and his Yemeni guard died instantly.

No one has claimed responsibility but the security official said authorities were "assuming that al Qaeda was behind it".

"If this is the case, it would be the first time al Qaeda has used a car to carry out an assassination," he said. The official said previously militants have used motorbikes, often without licence plates.

AQAP, regarded as al Qaeda's strongest regional wing, has mounted operations in Saudi Arabia and tried to launch attacks against the United States.

Restoring stability in Yemen is an international priority because of its strategic position adjoining not only oil exporter Saudi Arabia but also major shipping lanes.

President Abd-Rabbu Mansour Hadi took over as head of state in a Gulf-brokered power-transfer deal in February, and later Yemen's army drove Islamist fighters out of southern strongholds in a military operation backed by the United States.

Washington has also stepped up drone strikes on suspected militants.

A Saudi official at the Foreign Ministry in Riyadh confirmed the Enizi's killing, the state news agency SPA said.

The Saudis are a major donor to their poor neighbour and hosted the signing of the deal for Hadi to take power.

Hadi, in a call to Saudi Interior Minister Prince Mohammed bin Nayef, described the attackers as "terrorists" and vowed to bring them to justice, the state news agency Saba said.

In October, masked gunmen shot dead a Yemeni man who worked in the security office of the U.S. Embassy in Sanaa, weeks after Abdulilah Al-Ashwal, a senior intelligence official, was killed in a drive-by shooting in the capital.

Islamists linked to al Qaeda are still holding the deputy consul at the Saudi mission in the southern city of Aden, whom they seized in March. They have demanded a ransom and the release of women prisoners held in the kingdom.