Hundreds of Yemeni tribesmen have joined raging protests at Sanaa University, which for weeks have been demanding the departure of President Ali Abdullah Saleh, an AFP correspondent saw Tuesday.
On the roads leading to the Sanaa University square, members of Yemen's tribes pitched tents marked with the names of their home provinces, which are concentrated in the north of the trouble-torn country.
Student-led protests demanding the ouster of Saleh, 32 years in power, erupted in the Yemeni capital since late January, inspired by the toppling of Arab autocrats in Egypt and Tunisia.
Dozens of anti-regime demonstrators were wounded on Sunday at the university square, which has become the nerve center of the capital's popular revolt, as police and regime loyalists unleashed tear gas and bullets in a bid to scatter protesters.
Security forces on Tuesday blocked all of the main arteries leading to the square except the north entrance in an effort to limit the influx of demonstrators.
Tribal chief Sheikh Amin al-Akeimi called on security forces to join "the revolution of the youth" and told AFP the powerful Baqil tribal confederation, which he represents, was "with the youth's revolution and ready to protect them."
"We ask the president to leave," he added.
Some leaders of the Hashid tribe, which is considered Yemen's most influential tribal confederation and includes nine clans, among them the Sanhan, long a bulwark of Saleh's regime, have also joined the ranks of the uprising.
Some 40 people have been killed in Yemen's protests that have been marred by violence.
The tribes, which have acted as a counterweight to government power in the past, hold considerable sway in Yemeni society where clan-affiliations remain important.