ADEN (AFP) - Authorities in Yemen's second city Aden shut its international airport on Wednesday in protest against attacks by Shi'ite militiamen on the president and other state figures.

Aden's main security body said in a statement that it was closing its airport, its seaport and entrances to the city due to "dangerous developments in the capital" and "attacks on the symbol of national sovereignty and constitutional legitimacy, President Abdrabuh Mansur Hadi."

The Shi'ite militiamen, known as Houthis, seized control of Yemen's presidential palace and attacked Hadi's residence Tuesday in what officials said was a bid to overthrow the government, drawing condemnation from the UN Security Council.

Aden is the main city in southern Yemen, which was an independent country from 1967 to 1990 and where a strong separatist movement still exists.

The Houthis have abducted Hadi's chief of staff, Ahmed Awad bin Mubarak, a southerner, and have encircled the residence of Prime Minister Khaled Bahah since Monday, in a push to extract changes to a draft constitution opposed by the militia.

"We hold the Huthis responsible for the safety of all symbols of constitutional legitimacy," the statement said, naming Hadi, Bahah and Mubarak.

Aden's security committee urged the international community and regional governments to "carry out their duties" in defending "constitutional legitimacy" in Yemen.

Hundreds of pro-government militias, known as Popular Committees, arrived in Aden from several southern provinces, in coordination with the army, to protect government institutions and vital installations there, residents told AFP.

The capital Sanaa appeared quiet on Wednesday after Shi'ite militia chief Abdul Malik al-Huthi warned that "all options are open" in regards to Hadi and that "no one, the president or anyone else, will be above our measures if they stand to implement a conspiracy against this country."