Yemeni air force officers shut down the capital's airport on Saturday, stopping all flights in protest at the sacking of their commander, a half brother of former President Ali Abdullah Saleh, an aviation official said.

A source on the military committee overseeing the armed forces' restructuring told Reuters the air force head, General Mohammed Saleh Al-Ahmar, had refused to leave his post unless General Ali Mohsen Al-Ahmar, an opponent of Saleh, was also fired.

The airport closure was a direct challenge to President Abd-Rabbu Mansour Hadi, who replaced Saleh earlier this year and is trying to push through a restructuring of the armed forces to remove Saleh allies from key posts.

The armed forces split during the lengthy uprising against Saleh's rule, with some units openly siding with protesters.

Military vehicles full of soldiers encircled Sanaa airport at dawn on Saturday, turning passengers away and preventing flights from taking off or landing, witnesses said.

Demonstrators demanding Saleh Al-Ahmar's resignation brought several Yemeni airports to a standstill earlier this year. Hadi dismissed him on Friday and gave him the post of assistant to the defence minister.

The airport closure highlights the challenges facing Hadi, whose reshuffle is upsetting the entrenched interests of Saleh's associates and those of General Ali Mohsen, some of whose allies were also sacked on Friday.

Mohsen turned against Saleh early last year along with part of the armed forces, sparking sporadic open combat on the streets of Sanaa with loyalist troops and tribal militiamen that threatened to push the country into civil war.

Transport Minister Waed Abdullah Bathib told Qatar's state news agency incoming flights had been diverted to the southern port city of Aden.

The reshuffle, which left Saleh's son and nephew in place as heads of key military units, was welcomed by United Nations and Gulf diplomats who helped hammer out the deal under which the former leader left office after months of anti-government demonstrations that paralysed the impoverished state.

The diplomats said Hadi's move was in 'perfect harmony' with the letter and spirit of the power transfer plan, according to a statement cited by state news agency Saba.

A committee responsible for demilitarising Sanaa was dismantling checkpoints set up by the warring factions in the west of the city to enforce the withdrawal of armed tribesmen and troops from the streets by the end of the week. Previous efforts to do this have failed.

Hadi faces a sectarian rebellion in north Yemen and an emboldened wing of al Qaeda concentrated in the south, which is also home to a separatist movement trying to revive a socialist state that Saleh united with the north in 1990.

Yemen's state news agency was hacked on Saturday, apparently by southern secessionist sympathisers. Instead of the usual news feed, there were pictures of southern leaders and the former state's flag.

'Your turn has come, all major Yemeni websites. If we do not see the southern flag waving above Yemeni sites we will eventually destroy them,' read a statement posted on the site.

Some southerners accuse northerners of usurping their resources and discriminating against them. They want no part in the united Yemen envisaged by the Gulf initiative. - Reuters