SANAA - At least eight Katyusha rockets were fired Monday evening at a base of defected Yemeni troops and nearby residential areas in northwest Sanaa, killing at least three people, injuring many others and causing big fire, dissident soldiers and residents told Xinhua. ?

"Three Katyusha rockets hit this evening the northern part of the base of the First Armored Division led by defected Major General Ali Mohsen al-Ahmar in the northwest of the capital Sanaa, killing and injuring dozens of pro-protest soldiers," a colonel at the base told Xinhua on condition of anonymity.

"The rockets were fired from a Republican Guards' military base located in Al-Subaha Mountain, a few kilometers west of al-Ahmar's military base," the colonel said.

Local residents told Xinhua that some four-meter-long rockets hit the residential area near the military base, causing big fire and forcing residents to flee their homes.

Another four rockets struck a residential area and a mosque near opposition-run Islamic Eyman University, both located exactly south of the military base, according to residents.

"At least three civilians were killed, two from one family, and several others were severely wounded," two residents of the area told Xinhua.

"Many families in the area and students of Eyman University were fleeing, as more defected soldiers were deployed there and alerted the residents that more attacks are expected in the next few hours," they added. ?

Earlier Monday, Yemeni government forces killed at least 31 people, including three dissident soldiers, in the second day of clashes with defected army and protesters in the capital Sanaa and the southern province of Taiz, bringing the death toll over two days to 57, medics and witnesses said.

The deadly clashes raged on as UN envoy to Yemen Jamal bin Omar and Abdullatif al-Zayani, chief of the Gulf Cooperation Council ( GCC), arrived in Sanaa Monday on official visits.

The visits are aimed at pushing forward a GCC-brokered power transition deal between President Ali Abdullah Saleh and the opposition, as well as helping calm down the escalated tension, according to Yemen's government officials.

Saleh, who had backed out of signing the GCC deal for three times, is still in Saudi Arabia rehabilitating from injuries he sustained in an attack on his palace in early June.

Yemen has been gripped by a political crisis since protests erupted across the country in late January, which demanded an immediate end of the 33-year rule of Saleh.