SANAA, Yemen – Suspected al-Qaida gunmen killed five soldiers early Sunday in a southern province of Yemen, an official said, as U.S. embassies across the Muslim and Arab world reopened after terror threat emanating from the region.

The U.S. Embassy in Yemen’s capital, Sanaa, remained closed Sunday. Eighteen other diplomatic posts Middle East and Africa were to reopen, the State Department said, though the Muslim holiday of Eid al-Fitr saw many businesses closed.

An intercepted message between al-Qaida officials about plans for a major terror attack triggered the closures.

On Sunday, attackers in Yemen surprised the soldiers at their post guarding oil and gas projects in Shabwa, an official said.

Pipelines carrying oil and gas to coastal terminals in Yemen’s mostly lawless south have been repeatedly attacked by al-Qaida militants and tribes with whom they have ties. Yemeni officials also suspect tribesmen allied with former President Ali Abdullah Saleh.

There has been a spike in the last two weeks in suspected U.S. drone strikes in the country targeting al-Qaida. Yemeni officials say nine attacks have killed 38 alleged militants.

An accelerated use of drone strikes in Yemen under President Barack Obama and a U.S.-backed offensive last year drove militants from territory they had seized a year earlier, during Yemen’s turmoil amid the Arab Spring.

The U.S. considers the local al-Qaida branch, also known as al-Qaida in the Arabian Peninsula, to be the world’s most active.