* Most dead are victims of mob violence
* Large rebel convoy seen leaving capital Bangui
* U.S. warns of targeted sanctions
* Amnesty warns of violence risk in northern towns (Adds U.S. threatening targeted sanctions)
By Emmanuel Braun
BANGUI, Jan 26 (Reuters) - At least eight people were killed in mob violence in Central African Republic's capital, Bangui, on Sunday as senior officers from the Seleka rebel movement fled the city, according to the country's Red Cross and a rights group.
Almost 1 million people, or a quarter of the population, have been displaced by fighting that began when the mainly Muslim Seleka rebels seized power in the majority Christian former French colony in March.
Christian self-defence groups, known as "anti-balaka", or anti-machete, have since taken up arms against them.
U.S. Secretary of State John Kerry warned on Sunday that Washington was prepared to impose targeted sanctions against those responsible for the religious-based violence .
The United Nations estimates that more than 2,000 people have been killed since March in tit-for-tat bloodshed that a French intervention force and thousands of African peacekeepers have failed to stop.
"Today there were eight dead. Only one was shot. The rest were killed with primitive weapons. We even had one woman whose throat was slit," Antoine Mbao Bogo, president of the country's Red Cross, told Reuters.
Seven others were injured in Sunday's violence, he said.
Kerry said the United States was deeply concerned with the escalation in clashes.
"The United States is prepared to consider targeted sanctions against those who further destabilize the situation, or pursue their own selfish ends by abetting or encouraging the violence," Kerry said in a statement.
"Preventing the violence from gaining further momentum and costing more lives will require all of CAR's leaders, past and present, to be clear in condemning it," he said.
It was not immediately clear why the rebel leaders, who were travelling in a convoy of more than two dozen vehicles, left Bangui or where they were heading.
Central African Republic swore in new interim President Catherine Samba-Panza on Thursday, replacing Michel Djotodia, a former Seleka leader, who stepped down on Jan. 10 under intense international pressure.
A heavily armed Seleka convoy left Bangui on Sunday, escorted by Chadian soldiers from the country's African Union peacekeeping force, a human rights campaigner told Reuters.
"In the middle of the convoy, I saw several Seleka generals, including the head of military intelligence," said Peter Bouckaert, emergencies director for Human Rights Watch, who saw the convoy 60 km (37 miles) north of the city. "It feels a bit like the endgame for Seleka in Bangui."
Many Seleka fighters, a large number of whom came from neighbouring Chad and Sudan, have abandoned the capital in recent months following the deployment of French troops.
NO END IN SIGHT
Samba-Panza has pledged to hold talks with armed groups in an effort to restore order and used her inaugural address to plead for militia to lay down their arms to halt the escalating inter-religious violence.
But lynchings and looting, particularly targeting Bangui's predominantly Muslim neighbourhoods, have continued unabated even after deployments of French and African troops in the city.
A Reuters witness saw the bodies of two victims of a mob attack burning in the street in Bangui's Castor district.
"The youth in the neighbourhood saw the men here. They called them over, and they ran away. They caught them just right here and killed them," said a young man who gave his name only as Alex.
Another witness reported heavy fighting with automatic gunfire and rocket-propelled grenades between Seleka fighters and anti-balaka in the PK12 neighbourhood. A senior humanitarian official said other clashes occurred in the Miskine neighbourhood.
The violence has swept across the countryside outside of the capital where international peacekeepers are less present.
On Sunday, Amnesty International warned of the potential of large-scale killing in the northwestern towns of Baoro and Bossemptle, where civilians were killed and hundreds of homes were burned last week.
"There is a huge risk of a major human tragedy because of the complete absence of any peacekeeping force," Amnesty senior crisis adviser Donatella Rovera said in a statement.
"Peacekeepers were sent to the CAR with a clear mandate: to protect civilian lives. They must not fail it."
(Additional reporting and writing by Joe Bavier; Additional reporting by Lesley Wroughton in Washington; Editing by Mark Heinrich and Peter Cooney)