By Paul-Marin Ngoupana

BANGUI (Reuters) - Rebels pushed closer to the capital of Central African Republic on Wednesday despite a military intervention by neighboring Chad meant to halt their rapid advance in the mineral-rich country.

The insurgents, who have threatened to unseat CAR's president unless he honors a five-year-old peace deal, said they seized that town of Kabo, around 400 km (250 miles) north of the capital Bangui in the morning.

Rebel Colonel Joseph Zoundeko told Reuters his men had already started pushing further south and warned forces from CAR's ally Chad, who crossed into the country on Tuesday, to stay away.

"Kabo is under our control since this morning ... We quickly routed the government troops present in the town, killing 12 and taking six prisoners," he said.

"We ask (Chadian president Idriss) Deby not to get mixed up in our affairs ... His troops must keep away from our positions," Zoundeko added.

A United Nations official confirmed the fall of Kabo, the latest in a string of towns taken by the insurgents since they launched their offensive further in the north and northeast of the chronically unstable country last week.

The fighting has already forced thousands of civilians to flee their homes, The International Committee of the Red Cross said.

REBEL ALLIANCE

CAR's government on Wednesday said its army had made a strategic retreat in some areas but had not been driven out of the north.

"The military offensive led by our forces with the Chadian army ... have indeed allowed us to begin the reconquest and control of the attacked zones," it added in a statement, without going into further detail.

Around 20 vehicles carrying soldiers from CAR's northern neighbor Chad crossed the border on Tuesday to help push back the rebels, government and U.N. officials said. There were no reports of them clashing with the insurgents.

Zoundeko said he was part of a rebel alliance known as Seleka and made up of breakaway factions from the CPJP, UFDR and CPSK - groups which signed a 2007 peace deal.

The rebels on Monday demanded the government free prisoners and pay rebel soldiers money promised to them in the agreement, among other demands.

Long-running instability in landlocked CAR, roughly the size of former colonial master France, has discouraged major investment in its timber, gold, uranium and diamond deposits.

A mix of local rebellions, banditry, ethnic tensions and the spill-over of conflicts in neighboring Chad, Sudan and Democratic Republic of Congo have undermined efforts to stabilize the nation since independence in 1960.

President Francois Bozize took power in a 2003 coup with support from Chad's President Idriss Deby and won a new mandate in January 2011 elections which opponents dismissed as fraudulent.

The two leaders remain close allies, and Chad has intervened in CAR on several occasions in support of Bozize.

(Additional reporting by Stephanie Nebehay in Geneva; Writing by Joe Bavier; Editing by Andrew Heavens)