Yemen's parliament failed Sunday to discuss the president's resignation, extending a dangerous power vacuum, as US President Barack Obama vowed to still pursue Al-Qaeda in the country despite the crisis.

President Abdrabuh Mansur Hadi, a key US ally in the fight against Al-Qaeda's Yemeni franchise, tendered his resignation Thursday along with Prime Minister Khalid Bahah, saying he could no longer stay in office as his country was in "total deadlock".

Obama described Yemen as a "dangerous part of the world," saying his priority was to ensure Americans' safety, but he denied reports of the suspension of US drone strikes against jihadists in the country.

"We continue to go after high-value targets inside of Yemen and... we will continue to maintain the pressure that is required to keep the American people safe," he said in New Delhi.

Obama's remarks came as a powerful Shiite militia fired warning shots to disperse a protest against their takeover of Sanaa.

The Huthi militia, who have controlled most of the capital since September, overran the presidential palace last week, prompting Hadi to step down, shortly after Bahah quit.

As demonstrators gathered near Sanaa University, the militiamen fired warning shots to disperse them, before detaining several people.

The militiamen also attacked journalists and smashed their cameras, before deploying in force to prevent any renewed protests.

The journalists' union told AFP the militia detained three Yemeni newsmen covering the protest, and that female freelancer Huda al-Zabhani was beaten up.

One of the three, Reuters photojournalist Mohammed al-Sayaghi, said he was released after being held for an hour of questioning.

On Saturday, thousands of Yemenis took to Sanaa's streets to demand Hadi retract his resignation, which parliament has to approve, in the biggest anti-Huthi demonstration to date.

The crisis in the Arabian Peninsula country escalated on January 17 when the Huthis seized Hadi's chief of staff, Ahmed Awad bin Mubarak, in an apparent bid to extract changes to a draft constitution.

The Huthis still hold Mubarak and maintain a tight grip on the capital despite a deal struck late on Wednesday to end what authorities called a coup attempt.

The fall of Hadi's Western-backed government would raise fears of complete chaos engulfing Yemen, strategically located next to oil-rich Saudi Arabia and on the key shipping route from the Suez Canal to the Gulf.

On Sunday, parliament for a second time postponed an extraordinary session which had been due to discuss Hadi's resignation.

Parliament "decided to postpone an emergency meeting set to take place on Sunday... to another date which will be decided later to make sure all members are informed to attend," state news agency Saba reported.

Lawmakers had originally been due to meet on Friday to discuss his request to step down.

The Shiite militiamen, who hail from Yemen's northern highlands and belong to the Zaidi branch of Shiism, have surrounded the parliament building since late Thursday, two days after they seized control of the presidential palace.

The Huthis have also encircled Hadi's residence and those of several ministers.

"We are under house arrest," a minister of state in the resigned government, Hasan Zaid, himself a Zaidi, told AFP.

The Huthis blocked a convoy of armed Sunni tribesmen who arrived Saturday in Sanaa to attempt to free top officials, tribal sources said.

The latest developments have fuelled fears of a paralysis in the central administration, with government employees unsure if they will be paid at the end of this month.

"There is no security and no business as people are afraid of buying anything in this situation. I'm having to close my shop early every day," said a shop-owner in central Sanaa, Ahmed al-Wasabi.

Queues have formed outside petrol stations for fear of the worsening security triggering shortages.

Oxfam said 16 million Yemenis -- more than half the population -- were in need of aid.

"A humanitarian crisis of extreme proportions is at risk of unfolding in the country if instability continues," the charity said.

In the south, a soldier was killed and three wounded as troops stopped southern separatists from setting up a checkpoint in the main city of Aden, security officials and witnesses said.