Students shout slogans as they protest on the Sanaa University campus to show their support for a boycott of university studies as part of protests demanding the resignation of Yemeni President Ali Abdullah Saleh, in Sanaa,Yemen, Sunday, Sept. 18, 2011. The Arabic on banners at left reads, “for the blood of the martyrs, I will convey my revolution from inside the university to each house.” – AP Photo/Hani Mohammed

SANAA: Fighting broke out in a northern district of the Yemeni capital Sanaa on Sunday, the latest breach of an uneasy ceasefire between tribesmen opposed to President Ali Abdullah Saleh and troops loyal to him.

Shelling could be heard near the home of a prominent anti-Saleh tribal leader in the Hasaba district, site of weeks of fighting that began in May and brought the impoverished Arab state to the brink of civil war.

The family of anti-Saleh tribal leader Sadeq al-Ahmar said the Republican Guard, commanded by Saleh's son, had shelled their house.

State media and a security source blamed the fighting on the tribesmen, who have sided with protesters demanding the resignation of Saleh, saying they had attacked the Interior Ministry building in Hasaba armed with a variety of weapons.

Several civilians were hurt in the attack by the tribesmen, state television said.

Tensions that have been bubbling in the past week have led to two earlier outbreaks of fighting in the capital.

On Thursday, mediators from neighbouring Saudi Arabia intervened to help end the street fighting, which was the fiercest in recent weeks, diplomatic sources said.

Saleh, recovering in Saudi Arabia from a June assassination attempt, is holding on to power despite international pressure to quit and eight months of protests against his 33-year rule.

The United States and Saudi Arabia fear unrest in Yemen will embolden al Qaeda's Yemen-based regional wing to launch strikes in the region and beyond.