Thousands of residents are fleeing Sanaa, the Yemeni capital, as fighting between opposition tribesmen and loyalist troops of president Ali Abdullah Saleh rages on.

Much of the fighting, which began late on Wednesday night, occurred in the Hasaba district of northern Sanaa, where Sheikh Sadiq al-Ahmar, the powerful leader of the Hashed tribal confederation, has his base.

Yemen’s defence ministry said the Special Forces, headed by Saleh’s son Ahmed, have been deployed to “liberate” buildings held by al-Ahmar’s fighters.

Medics in Sanaa told the AFP news agency that 15 people had been killed in the overnight clashes, including a seven-year-old girl hit by a stray bullet.

They have yet to receive word on casualties from Thursday’s fighting as ambulance crews were unable to access the neighbourhood.

Hakim Al Masmari, editor of the Yemen Post, told Al Jazeera that an estimated 2,000 additional fighters "armed and ready to fight" have entered Sanaa to reinforce the Hashed confederation.

"We expect [the tribal fighters] to take control of different government complexes [in Sanaa]," Al Masmari said.

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Witnesses near the Hasaba district said they heard several blasts but were not sure of the cause or damage.

"There are very powerful explosions. Sounds like missiles or mortars. May God protect us," a resident said.

One Sanaa resident told AFP that he and 30 members of his household were trying to flee Sanaa like the city’s many others.

"Sanaa is deserted now and if these battles continue, Yemen will be finished," he said.

Many shops were closed and long queues formed outside petrol stations. Residents who had remained complained of water shortages and power cuts.

Main flash points

Sanaa residents said Thursday’s fighting was the fiercest since the mostly peaceful street protests demanding an end to Saleh’s 33-year rule started nearly four months ago.

Fresh fighting ensued after a fragile truce between al-Ahmar’s forces and embattled Saleh collapsed on Tuesday.

This week, there have been three main flash points in the country - the fighting in the capital, government troops firing on protesters in Taiz in the south and a battle with fighters in the coastal city of Zinjibar.

Sanaa’s Hasaba has been the focal point of armed clashes over the past week that have killed at least 115 people and pushed the country closer to civil war.

Residents also reported overnight fighting near Sanaa airport, which was closed briefly last week during skirmishes between Saleh's forces and Hashed rebels.

Passengers said flights were suspended for several hours at Sanaa airport on Thursday, but the airport reopened later in the afternoon.

But Naji al-Marqab, director of the airport, denied that flights had been suspended and diverted to the southern city of Aden, insisting that air traffic was running normally.

The fighting on Thursday came as US envoy John Brennan left Saudi Arabia for the United Arab Emirates to reportedly seek help in stopping a civil war in Yemen, the Reuters news agency reported, citing an unnamed US official in Saudi Arabia.

The US and others have been pressing Saleh to accept a Gulf-led agreement to step down. Saleh has agreed to the deal three times, only to renege at the last minute.

Source: Al Jazeera and agencies