(CNN) -- Government troops fought fresh battles with opposition fighters in Yemen's capital, Sanaa, early Friday as the country's embattled president tried to put down a tribal revolt.
Troops backed by tanks were nearing the home of tribal leader Sadeq Al-Ahmar, whose followers have been battling troops loyal to President Ali Abdullah Saleh for nearly two weeks, witnesses reported. The nearby headquarters of Yemen's national airline was ablaze, with surrounding houses catching fire as well, witnesses said.
Government spokesman Abdu Ganadi told CNN said Saleh's forces "are near victory." But Abdulqawi Al-Qaisi, a spokesman for Al-Ahmar, said "All government claims of victory are fabricated, and our forces are still on the ground."
And in Change Square, where tens of thousands of anti-government protesters have made camp, witnesses said gunmen on surrounding streets were firing into the crowd, while snipers were visible on nearby rooftops.
"It's very tense inside Change Square now, because there is a fear that government forces might attempt to come into Change Square and take it over at any time," one of the protesters, who asked to remain anonymous due to security concerns, told CNN. A nearby resident said the fighting had subsided after midnight, however.
"We're still hearing bombs and gunfire, but not as much as we were just an hour ago," the resident said.
The fighting erupted May 23, after Saleh balked at a deal negotiated by Persian Gulf states that would have eased him from office in 30 days. The intensity of the fighting in the capital, where most of Yemen's security forces and army units are based, has increased fears that the country is on the verge of civil war.
Saleh has ruled Yemen since 1978, and the nation has been a key U.S. ally in the battle against the al Qaeda terrorist network. But Yemen was caught up in the wave of protests that swept the Arab world after the January ouster of Tunisia's longtime strongman, leaving Saleh battling both peaceful and violent resistance movements.
The impoverished, arid and mountainous nation has a weak central government and contains vast stretches where tribal law reigns supreme. A fresh group of about 1,000 armed tribesmen were seen entering Sanaa early Thursday, Sanaa resident Nageeb Mujaili said.
"We asked them why they were going to Sanaa armed," said Mujaili. "And they said to support their leader, Sheikh Sadeq Al-Ahmar."
Yemeni state television reported that government forces had beaten back tribal fighters from areas of the capital near the Ministry of Tourism building on Thursday, and Sanaa residents reported hearing explosions near the presidential palace, a government source said.
"The reason the street fighting in Sanaa has gotten a lot more intense in the past several hours is because special forces are now involved," said the source, who asked not to be identified because he is not authorized to speak to the news media.
"The special forces of the Republican Guard, the elite units, got involved on Wednesday. They're being used because the government wants to minimize collateral damage and the special forces have particular training in clearing fighters from buildings."
A security official at Sanaa International Airport said inbound and outbound flights were halted due because of security concerns over clashes near the airport. But the official, who is not authorized to speak to the media, said that the airport itself is not closed.