Yemeni troops fired on an opposition protest camp in the capital, Sana'a, just a day after President Ali Abdullah Saleh had called for a truce and an end to the fighting.

Loyalist troops fired on anti-government protesters in ''Change Square” early Saturday killing at least 17 people and injuring more than 25 others. Elsewhere in the capital, troops loyal to the president shelled the headquarters of the 1st Armored Division, who sided with the demonstrators, leaving 11 dead and 112 injured.

Mr. Saleh arrived in Yemen Friday from Saudi Arabia, where he had spent three months recovering from injuries sustained in an attack on his presidential compound in Sana'a.

In a statement after his return, the president said the solution to Yemen's mounting anti-government unrest was dialogue — not “guns and cannons.” He urged government and opposition forces to observe a truce and ceasefire.

Protests against the embattled president have escalated over the past week, with clashes leaving more than 128 people dead.

In recent days, Yemen's political parties said they were working on a plan to force Mr. Saleh out of power.

Earlier this week, representatives of the six-nation Gulf Cooperation Council met with Vice President Abed Rabbo Mansour Hadi in Sana'a in an attempt to revive a long-stalled plan that calls for President Saleh to hand over power to a deputy.

The U.S. White House on Friday urged Mr. Saleh to begin a “full transfer of power.”