Gunmen have seized Yemeni president Abdrabuh Mansur Hadi's chief of staff, in a new challenge to his leadership of the country.

Ahmed Awad bin Mubarak's nomination as prime minister last year was rejected by Shiite militiamen controlling the capital.

"An armed group set up a checkpoint in Hada," a southern district of Sanaa, and "captured Mubarak with his companions," an official from the national dialogue secretariat told AFP.

The senior politician was "driven away to an unknown location," the official said, adding that the abductors "are suspected of being [Shiite] Huthi militiamen".

Mr Mubarak is secretary-general of the national dialogue on a political transition following the 2012 resignation of veteran president Ali Abdullah Saleh after a bloody year-long uprising.

Yemen has been dogged by instability since Mr Saleh's ouster, with the Huthis and Al Qaeda seeking to fill the power vacuum.

The Huthis are widely believed to be backed by Mr Saleh.

Al Qaeda in the Arabian Peninsula (AQAP) also has a record of acting well beyond its Yemeni base, and claimed responsibility for the January 7 attack on French satirical magazine Charlie Hebdo that killed 12 people.

Yemeni authorities said on Saturday they had arrested two Frenchmen for questioning over suspected Al Qaeda links.

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The Charlie Hebdo attackers, French brothers Said and Cherif Kouachi, are known to have trained with Al Qaeda in Yemen.

"There are around 1,000 Al Qaeda militants in Yemen from 11 Arab and non-Arab countries," national security service chief General Mohammed al-Ahmadi said.

Mr Ahmadi said talks were under way to secure Mr Mubarak's release.

In a statement, the militia said Mubarak's detention was necessary to prevent a UN-brokered agreement between the presidency and them in September "from being broken," without clarifying Mubarak's role.

The "national peace and partnership agreement" was signed in September as the Huthis overran Sanaa.

It called for forming a new government and appointing Huthi advisors to president Hadi, and for Shiites to withdraw from key state institutions they had seized.

Mr Mubarak's kidnap came just before a meeting of the national dialogue secretariat to present a draft constitution that stipulates dividing Yemen into a six-region federation, which the Huthis oppose.

Political sources told AFP representatives of the Huthis and Mr Saleh's General People's Congress party walked out of a meeting headed by Mr Hadi on Saturday to discuss the political process, including the constitution.

The Huthi statement warned Hadi of an unspecified "series of special measures" they are planning, adding that "president Hadi must not cover up corruption".

Mr Hadi has struggled to assert his authority since the Huthis seized Sanaa.

AFP