Rebels have seized control of Yemen's state-run media and surrounded the Republican Palace where the Prime Minister lives, according to a government spokesman.

Gunfire and explosions have echoed across the city, with Yemen's military battling Houthi militia on the streets of the capital, Sanaa.

Earlier on Monday, the convoys of the Prime Minister and a top presidential adviser affiliated with the Houthis also came under fire, information minister Nadia Sakkaf said.

At least five people are reported to have been killed and 20 injured in the current unrest, although that figure is expected to rise.

The clashes - largely centred on the palace and a military area south of it - have been described as a coup attempt by the powerful Houthi movement.

"If you attack the presidential palace ... This is aggressive, of course it is an attempted coup," the information minister said.

Witnesses said fighting broke out shortly after 6am local time (9am UK time) and raged for several hours.

It is unclear what triggered the violence, although one witness said fighting began when a shell hit a hill in part of the city controlled by the Houthis.

The fighting marks the biggest challenge to the government of President Abd-Rabbu Mansour Hadi since the Houthi seized parts of Sanaa in September.

The Houthis had promised to withdraw their fighters as part of a United Nations-brokered peace deal in which President Hadi agreed to form a new national unity government.

Both sides accuse one another of failing to implement the terms of the deal.

Ongoing fighting is further complicating the country's efforts to battle the growing threat posed by al Qaida's Yemeni affiliate, al Qaida in the Arabian Peninsula.

It has been linked to numerous attempted terror attacks in the West and has claimed responsibility for orchestrating the attack on the French magazine Charlie Hebdo, which left 12 people dead.