ADEN: A US drone killed at least six suspected Al Qaeda militants in southern Yemen on Wednesday, officials said, a day after US and British embassies evacuated some staff because of growing fears of attacks.

It was the fifth strike in less than two weeks and follows warnings of potential attacks by militants that pushed Washington to shut missions across the Middle East, and the United States and Britain to evacuate staff from Yemen.

Witnesses and local officials in the province of Shabwa said the drone fired at least six missiles at two vehicles in a remote area some 70 kilometres north of the provincial capital, Ataq. Both vehicles were destroyed.

Residents who rushed to the scene found only charred bodies, they said.

At least 20 suspected militants have been killed since July 28, when a drone strike killed at least four members of Ansar al-Sharia, a local militant group affiliated to Al Qaeda in the Arabian Peninsula (Aqap), one of the most active branches of the network founded by Osama bin Laden.

Yemen, one of the poorest Arab countries, is one of handful of countries where Washington acknowledges targeting militants with strikes by drone aircraft, although it does not comment publicly on the practice.

US sources have told Reuters that intercepted communication between Osama’s successor as Al Qaeda leader, Ayman al-Zawahri, and the Yemen-based wing was one part of the intelligence behind the alert last week that prompted the closure of the embassies.

Security in Yemen is a global concern. Home to Aqap, considered one of the most aggressive branches of the global militant organisation, it shares a long border with Saudi Arabia, a US ally and the world's top oil exporter.

The US government supports Yemeni forces with funds and logistical support.

Yemeni authorities issued a statement early on Tuesday listing 25 “most wanted terrorists” it said were planning to carry out attacks in the country during the Eidul Fitr holiday this week. They also offered a five million Yemeni riyals ($23,000) for information leading to their capture.

A September11 attack last year killed the US ambassador to Libya and three other Americans in Benghazi.

US Republican Senator Lindsey Graham told CNN at the weekend that the recent actions taken to close the embassies showed President Barack Obama's administration had learned lessons from Benghazi.