Beleaguered President Abedrabbo Mansour Hadi, who fled to Aden after escaping from Shiite militia controlling Sanaa, considers the southern port city to be Yemen's capital, an aide said on Saturday.

But tensions were running high in Aden, as special forces suspected of links to the militia known as Huthis readied defences against an anticipated assault by Hadi loyalists.

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

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

But the United States, the first to close its mission in Sanaa, has said it will not do so, although it continues to back Hadi.

Hadi also accused ex-president Ali Abdullah Saleh and the Huthis of links with Iran, and spoke of his escape from Sanaa and Huthi demands to integrate thousands of their militants into the army and police and secure top government posts.

His remarks about Aden reflect his determination to hold out against Huthi efforts to extend their influence, but are purely symbolic because moving the capital requires a change to the constitution.

Outgoing defence minister General Mahmud al-Subaihi also managed to flee from Sanaa to Aden on Saturday, a source close to him told AFP.

"After realising he had disappeared from Sanaa, the Huthis broke into his house and searched it," said another source in his entourage, confirming his flight from the capital.

Subaihi was part of the government of prime minister Khalid Bahah, who resigned in January after the Huthis seized the presidential palace and key government buildings. The Huthis had named Subaihi to chair their new security commission.

The special forces commander in Aden, Abdel Hafez al-Saqqaf, has defied a decree by Hadi sacking him and said he will only follow orders from the presidential council in Sanaa.

His men have cut roads leading to their headquarters near Aden's international airport and set up barricades, saying they fear an assault by the Popular Resistance Committees, loyal to Hadi.

Aden, the country's second largest city, was capital of a once-independent south Yemen.

- Huthis' demands -

The Huthis named a "presidential council" after Hadi and Bahah tendered their resignations in January in protest at what critics branded an attempted coup.

After fleeing house arrest in Sanaa, Hadi resurfaced in Aden where he retracted his resignation. Bahah remains trapped in the capital.

On Saturday, Hadi said he escaped his Sanaa residence through a tunnel linking it to the nearby house of one of his sons and travelled to Aden using back roads.

The Huthis overran Sanaa in September and have since exerted their influence over several other areas.

The Shiite militia has long complained of marginalisation and fought the government between 2004 and February 2010.

The Huthis oppose a plan for a six-region federation, which Hadi hopes to implement, saying it would divide Yemen into rich and poor areas.

Hadi said Saturday the Huthis had demanded 135 top government jobs and the vice presidency for one of their leaders, Saleh al-Sammad.

They also demanded that 35,000 militiamen be integrated into the armed forces and 25,000 into the police.

Hadi accused Iran of links with the Huthis, saying 1,600 militia members are being trained in religious schools in the holy Iranian city of Qom.

He also accused Saleh, the veteran ex-president who was forced from power in 2012, of having urged Iran to persuade the Huthis to collaborate with him before they seized Sanaa.

The Gulf Cooperation Council, which continues to support Hadi, is ruled by Sunni Muslim regimes deeply suspicious of the Huthis, fearing they will take Yemen into Shiite Iran's orbit.