Saleh returned yesterday after a three-month absence in Saudi Arabia recovering from injuries sustained during an attack on his palace on June 3 "carrying the dove of peace and an olive branch".
Hours later however, members of the elite Republican Guard led by his eldest son Ahmed were fighting dissident troops protecting anti-government protesters in the north of the capital Sanaa.
Saleh arrived in the city on Friday during a sixth straight day of deadly clashes between troops loyal to him and heavily armed opponents.
But even as 69-year-old Saleh called for a ceasefire and talks, Washington urged the veteran president to step down.
In the latest violence, troops to loyal Saleh killed at least five anti-government protesters early Saturday in an attack on Change Square, the epicentre of anti-government protests, witnesses told AFP.
Soldiers launched the attack a little after midnight Friday, opening fire with guns and shelling the square, which protesters first occupied back in January. Snipers also targeted the people in the square from buildings around it, witnesses said.
"At least five protesters were killed," said a medic at a field hospital set up in the square.
In the streets nearby, the president's soldiers fought with dissident troops commanded by rebel General Ali Mohsen al-Ahmar.