Yemen's Defence Minister Mahmoud al-Subaihi has escaped from house arrest in the capital, Sanaa, controlled by Houthi rebels.

He had been placed under house arrest by the Shia rebels who seized the capital and took over the government in a coup on February 6.

Al-Subaihi is thought to be on his way to the southern city of Aden where Abd-Rabbu Mansour Hadi, recognised as president by regional powers, has set up his government.

The Western-backed leader, who fled to Aden after escaping from the Houthi custody, considers the southern port city to be Yemen's capital, a top aide said.

"Aden became the capital of Yemen as soon as the Houthis occupied Sanaa," the aide quoted Hadi as saying in reference to their takeover of the capital several months ago.

The remarks about Aden reflect Hadi's determination to hold out against Houthi efforts to extend their influence, but are purely symbolic because moving the capital requires a change to the constitution.

Aden, the country's second largest city, was capital of a once independent south Yemen, before unification in 1990, when Sanaa became the unified country's capital.

Hadi himself escaped house arrest in Sanaa two weeks ago, traversing a tunnel linking his house to the nearby house of one of his sons and then travelling to Aden using back roads.

Several Gulf states, including Saudi Arabia, have already moved their embassies to Aden after an exodus of foreign diplomats from Sanaa in February over security concerns.

In Sanaa, the Houthis named a "presidential council" after Hadi and Prime Minister Khalid Bahah tendered their resignations in January in protest at what critics branded a coup.