SANA'A // Thousands of armed tribesmen poured into Sana'a yesterday, engaging government troops in furious gun battles and promising 40,000 reinforcements were on the way.
It was the third straight day of intense fighting across Yemen and more and more citizens are fleeing the violence, fearing for their lives amid the likelihood of all-out civil war.
In the capital, witnesses said street battles lasted for more than 12 hours between the forces of President Ali Abdullah Saleh and tribesmen loyal to Sheikh Sadeq al Ahmar, head of the powerful Hashed tribal bloc. Heavy artillery shelling was reported in several neighbourhoods.
The government last night denied reports that Sana'a airport had been closed and flights diverted to Aden as fighting raged only 500 metres from the terminal.
Tribal sources said at least 20 people were killed and 75 injured in yesterday's clashes, including an attempt by several thousand tribesmen armed with rocket-powered grenades and rocket launchers to enter the city from the north-east, where they were forced back by units from Mr Saleh's Republican Guard.
The Yemeni government refused to comment on yesterday's death toll, but a spokesman admitted tribal forces were encircling the city.
Both sides continued to blame each other for the escalating violence, which rights workers claim has killed at least 140 people this week.
The encroaching tribesmen, from Amran province, said those who marched on Sana'a were only a small force and more would follow this week.
Ali al Suraihi, a tribesman involved in yesterday's assault, said 40,000 additional fighters were prepared to storm the capital. "The tribes will continue entering Sana'a. The government has not seen anything yet. It continues to raid our leaders' homes and we will raid Saleh's palace if the attacks don't stop."
A spokesman for Sheikh al Ahmar claimed 6,000 tribesmen had entered Sana'a this week. He said fighters from other tribes had joined the Hashed camp in its campaign against the Saleh regime.
"Yemenis know who is bloodthirsty. Saleh called for this war two weeks ago, and tens of thousands of tribesmen are ready to fight for the sake of the right cause," Mr Qaisi said.
Block-to-block fighting has been reported in all districts of the city. Thousands of locals have evacuated their homes and left the city with no specific destination.
"Where can we go?" said Salma Aghbari, a mother of six who fled her home when one of her sons was hit in the shoulder by a stray bullet this week. "The entire country is in chaos."
Yemeni warplanes launched strikes yesterday on the town of Khamer, the home and stronghold of Sheikh al Ahmar. The attack killed four civilians and injured 25 others, medical sources in Khamer said.
"Khamer is the town where these gunmen are coming from. We raided the city to stop the flow of tribes to Sana'a," a defence ministry official said.
Military troops loyal to the dissident general Ali Mohsen also engaged government forces in Sana'a yesterday. Gen Mohsen's spokesman said the forces took action after the general's military base was attacked nine times in the past week by government missiles.
Witnesses said a force of more than 1,000 opposition soldiers battled Republican Guards. It was reported that General Mohsen's men overran the attorney general's building in Sana'a and that hundreds of his troops had taken up positions around the building last night.
"The general does not want to be involved in any clashes, but the attacks against his military site have been continuous," said an official in General Mohsen's office.
General Mohsen, a one-time ally of Mr Saleh, is Yemen's most powerful military leader and is said to have about 40,000 troops under his command. Experts see the involvement of the general as a turning point in the battle for Sana'a.
"General Mohsen is the only person in Yemen President Saleh fears. Saleh knows the dangers of the general," said Ali Jaradi, editor in chief of Ahale independent newspaper. "When he joins the fighting in full strength, Saleh will have no chance to stay in power."
Ali Abdul Jabbar, director of Dar Ashraf Research Centre, said that when General Mohsen defected from the military and joined the revolution it was a severe blow to Mr Saleh's grip on power.
"Saleh is scared of General Mohsen. He knows he is full of surprises. That is why he has been Yemen's most powerful general for 30 years," Mr Abdul Jabbar said.
The government said it would use force against anyone who causes instability to the country and in Sana'a specifically.
Tareq al Shami, spokesman for Mr Saleh's ruling General People Congress party, said the tribes were acting like "barbarians".
"Normal citizens do not attack public property. These tribesmen are criminals and will stand trial for the crimes they are committing and insecurity they create," he said.
In Taiz province, where protests had been peaceful despite government crackdowns, gun battles were reported for the first time yesterday between government troops and protesters.
"The government kills innocent protesters who are calling for peaceful transition of power. We will use force against any side that attempts to attack protesters," said an opposition combatant in Taiz.
Bushra Maktari, a human-rights activist in Taiz, said protesters were against the use of weapons in achieving their goals, but they could not ignore the government's assault on a protest camp that left 100 protesters dead in Taiz this week and as many as 1,000 injured.
"Those who were killed have family who want to avenge the death of their loved ones. The gunmen are not from the revolutionary youth, but they are people who lost a relative when the government opened fire on its own people," Mr Maktari said.
In Abyan province, Islamist militants maintained their control of the town of Zinjibar yesterday after fighting off government forces and airstrikes. A resident in Zinjibar said more than 600 homes had been destroyed by government warplanes.
The Maqateen seaport, a strategic harbour in the city of Shoqra, is also in the hands of Islamist forces.
The defence ministry said on its website that at least 70 people had been killed in Zinjibar during the past week of fighting. The government also claimed to have retaken a number of government buildings that had been captured by tribal forces.
There were reports late yesterday that Mr Saleh may be prepared to sign a Gulf Cooperation Council-brokered deal for him to step down. The GCC plan would initiate a peaceful transfer of power in return for the president being immune from legal prosecution. Mr Saleh has promised to sign the deal three times in the past only to back away each time.
As the fighting continues on at least three fronts, thousands of families are fleeing their homes. Those who remain said they live in fear.
"Every time we hear an explosion we think our house will be next," said Abdul Hakim Maskar, a resident in Abyan.