Yemen's President Ali Abdullah Saleh was injured, four of his guards were killed and the parliament speaker was left in critical condition after the presidential palace was shelled on Friday, Al Arabiya TV reported.

The prime minister was also injured in the attacks, as street fighting between Saleh's forces and a tribal federation heightened on Friday in the capital.

"The Ahmar [tribe] have crossed all the red lines," the General People's Congress Spokesman Tareq Al-Shami told AFP, blaming the attack on pro-opposition tribal chief Sheikh Sadiq al-Ahmar, whose forces are at war with troops loyal to President Ali Abdullah Saleh.