At least 14 government soldiers were killed and 38 others, including two civilians, were injured in clashes on Monday between government forces and tribesmen in Yemen's capital, an official of the interior ministry told Xinhua.

The official said the death toll of the armed tribesmen was still unknown.

The armed tribesmen, who are from the most powerful tribe in Yemen, took control of the ministry of industry and trade and the official Saba news agency after fierce clashes with local guards and government forces on Monday afternoon.

About 50 staff were still trapped in the news agency, while female journalists had been evacuated by Republican Guards, an official of Saba said.

He added that one journalist was slightly wounded during the clashes, and the government forces were on their way to rescue them.

Earlier, anti-government tribal forces besieged the ministry of religious endowment and Islamic affairs, ministry of industry and trade, Saba news agency and the Yemeni airways building, according to security official and witnesses.

An official of the ministry of industry and trade said that the militants fired at their building and killed all the guards.

Meanwhile, heavy gunshots and huge explosions were heard in downtown Sanaa and violent clashes erupted near the house of Sadiq al-Ahmar, a leader of the opposition and Yemen's most powerful tribe (Hashid), to which President Ali Abdullah Saleh himself belongs. Al-Ahmar announced that he joined the anti-government protests in March.

Sadiq al-Ahmar's neighbour told Xinhua that about 72 people from tribesmen and government soldiers were killed and tens of others injured on Monday.

More soldiers equipped with tanks, armored cars and other heavy weapons were sent to the site as armed forces of al-Ahmar's tribe were on their way to Sanaa.

"It is a civil war, and huge casualties are expected," an official of the interior ministry said.

Tensions soared in Sanaa since Sunday evening after the Yemeni Republican Guards forces stored a lot of weapons in al-Ramah School, next to al-Ahmar's house.

On Sunday, Yemen celebrated the 21st anniversary of country's reunification as situation slipped on the verge of bloody clashes between thousands of armed loyalists of Yemeni President Ali Abdullah Saleh and their rivals who packed the streets to demand an immediate end to Saleh's 33-year rule.

Saleh has thwarted the U.S.-backed Gulf Cooperation Council (GCC) deal three times since April as he refused to sign it on Sunday.