Seif has often been put forward as the regime''s face of reform. Several of the elder Gadhafi''s sons have powerfulpositions in the regime and in past years have competed forinfluence.
Seif''s younger brother Mutassim is the nationalsecurity adviser, with a strong role in the military andsecurity forces, and another brother Khamis heads the army''s32nd Brigade, which according to US diplomats is the besttrained and best equipped force in the military.
The clashes in Tripoli began Sunday afternoon, whenprotesters from various parts of the city began to streamtoward central Green Square, chanting "God is great," said one28-year-old man who was among the marchers.
In the square, they found groups of Gadhafisupporters, but the larger number of protesters appeared to betaking over the square and surrounding streets, he and twoother witnesses said.
That was when the backlash began, with snipers firingdown from rooftops and militiamen attacking the crowds,shooting and chasing people down side streets. they said.
"We saw civilian cars with Gadhafi pictures, theystarted to look for the protesters, to either run over them oropen fire with automatic weapons," said the 28-year-old,reached by telephone. "They were driving like mad mensearching for someone to kill. ... It was total chaos,shooting and shouting."
The witnesses reported seeing casualties, but thenumber could not be confirmed. One, who spoke on condition hebe identified only by his first name Fathi, said he saw atleast two he believed were dead and many more wounded. "Icould still hear gunfire after 5 am this morning," he said.
After midnight, protesters took over the main Tripolioffices of two state-run satellite stations, Al-Jamahiriya-1and Al-Shebabiya, one witness said. All the witnesses spoke oncondition of anonymity because of fears of retaliation.
After daybreak Monday, Green Square and surroundingstreets were empty. Schools, government offices and moststores were shut down across the city of 2 million, thewitnesses said.
State TV sought to give an air of normalcy, reportingthat Moammar Gadhafi received telephone calls of support fromthe presidents of Nicaragua and Mali. It showed footage of acrowd of Libyans said to be from the town of Zeltein chantingtheir support for Gadhafi in a conference hall.
Gadhafi, in flowing black and brown robes, waved tothe crowd with both hands. It was not clear when the scene wastaking place.
Western countries have expressed concern at the risingviolence against demonstrators in Libya. British ForeignSecretary William Hague said he spoke to Seif al-Islam byphone and told him that the country must embark on "dialogueand implement reforms," the Foreign Office said. (AP)