A US drone strike killed four suspected Al-Qaeda militants in Yemen early Tuesday, a tribal source said, amid heightened security across the Middle East against a possible major attack by the jihadist network.

Among those killed was one of 25 Al-Qaeda operatives listed late on Monday by the Yemeni authorities as among those plotting attacks to coincide with the ending of the Muslim holy fasting month of Ramadan later this week, the source told AFP.

The raid in Yemen's eastern Marib province targeted their vehicle "and turned it into a ball of fire, immediately killing the four militants," the source said, adding that all those killed were Yemenis.

Yemen's official Saba news agency confirmed "the death of four Al-Qaeda militants in Wadi Abida in Marib."

The tribal source named two of the dead as Saleh al-Tays al-Waeli and Saleh Ali Guti.

Waeli figures on a government list of 25 Al-Qaeda suspects wanted in connection with an alleged plot to launch a major attack before Ramadan ends and the Eid al-Fitr feast begins, either Thursday of Friday.

About two dozen US diplomatic posts have been shuttered across the Middle East since Sunday after Washington said electronic intercepts of high-ranking Al-Qaeda operatives signalled a major attack was imminent.

US media said Tuesday that intercepts between Al-Qaeda chief Ayman Al-Zawahiri and the leader of the group's Yemen affiliate had sparked the closures as well as a global travel alert.

The New York Times said that the electronic communications last week revealed that Zawahiri had ordered Nasser al-Wuhayshi, the head of Al-Qaeda in the Arabian Peninsula, to carry out an attack as early as this past Sunday. 

Tuesday's drone strike is the fourth of its kind since July 28. The raids have killed 17 suspects in one week.