Yemen's defence minister was set to resume his duties from second city Aden on Sunday after defecting from Shiite militia who control the capital, a source in the president's office said.

General Mahmud Subaihi's escape from Sanaa follows that of Western-backed President Abedrabbo Mansour Hadi, who has called on ministers to join him in the southern port city to reestablish the government if they can.

The minister made it safely to Aden but one of his guards was killed in a firefight with Huthi militiamen during the escape, an aide told AFP.

The militia had named Subaihi head of a new security committee when they completed their seizure of power in Sanaa in February.

The government in which he served tendered its resignation under militia pressure in January but it was never accepted by Hadi.

Prime minister Khalid Bahah and most other ministers remain under house arrest in the capital.

Subaihi's convoy made it to Aden without incident, arriving before dawn, his aide said.

One of his guards, who was travelling in a second convoy which left an hour later, was killed when it was ambushed by the Huthis near the central city of Taez.

The militiamen captured another five people travelling in the second convoy but later released them under pressure from local tribes, the aide added.

Hadi, who tendered his resignation in January, withdrew it after escaping to Aden last month saying it had been offered under militia duress.

The city, which was the capital of an independent south Yemen before its union with the north in 1990, is largely in the hands of troops and militia loyal to the president.

Hadi said on Saturday that he now regards it as the capital of the united country because of the militia's grip on Sanaa.