BANGUI - Rebels in the Central African Republic, defying regional mediation efforts, Saturday seized a new town in their advance on the capital Bangui and repelled a bid by army soldiers to retake a key central city.

The rebels faced no resistance as they entered the town of Sibut some 150 kilometres (95 miles) from Bangui, a military source told AFP.

Also Saturday, officials on both sides said the rebels of the so-called Seleka coalition had repelled army soldiers who were trying to recapture Bambari, a former military stronghold in the landlocked country, one of the world's poorest despite vast mineral wealth.

A military official described "extremely violent" fighting over the town, with detonations and heavy weapons fire audible to witnesses some 60 kilometres away.

Djouma Narkoya, a Seleka leader, claimed that the army suffered "losses", while the rebel side had "one killed and three injured" in the fighting.

The rebels, who launched their offensive in early December, now control four main towns, mainly in the north and centre of the country, including the garrison town and key diamond mining hub of Biraosince.

Bangui is in the southwest.

Meanwhile regional efforts to mediate a peaceful solution in the landlocked equatorial country were at a standstill.

A day after announcing that the rebels and the government had agreed to hold unconditional peace talks and that more regional troops would head to the country, the Economic Community of Central African States said no dates had been set for either measure. The bloc's foreign ministers will meet again next Thursday "and that is when they will announce a date for the meeting in (the Gabonese capital) Libreville," ECCAS's communications director Placide Ibouanga told AFP, referring to talks between rebels and the government.

He said the arrival of more regional troops was also uncertain.

"The arrival date of the new contingent depends on the heads of state," he said, referring to troops that are due to reinforce the 500-strong Multinational Force of Central Africa, which ECCAS deployed in the chronically unstable country in 2002.

The coalition of three rebel movements known as Seleka -- or the "alliance" in the Sango language -- says the government has not fulfilled the terms of peace pacts signed in 2007 and 2001, providing for disarmament and social reintegration for insurgents, including pay.

Central African President Francois Bozize, who took power in a 2003 coup, has twice been elected into office.

In the face of the rebel gains against an ill-equipped army, Bozize's appeals for help from former colonial power France and from the United States have fallen on deaf ears.

Neighbouring Chad, which has helped Bozize with rebellions in 2010, has sent a contingent to the country, however.

In Bangui, food prices have soared, further spiking tensions and uncertainty.

Residents feared a rebel advance on the city would make a deteriorating situation even worse.

"I'm afraid of the rebels coming," said vegetable vendor Euphrasie Ngotanga in the city's huge Sambo market. "We're not going to sell our produce if there's no peace. And then how we will feed our children?"

"We don't eat properly any more," said another vendor, Angele Bodero, with her baskets full of condiments before her. "Cassava has become more expensive, everything costs more," she said, referring to the country's staple food.

A bag of cassava has risen nearly 50 percent from 13,000 CFA francs to 18,000 FCFA (19.80 to 27.40 euros, $26 to $32).

"We need peace so we can work and get by," said elderly vendor Jean Guere, trying to sell the flour sifters he makes himself.

The United Nations has demanded rebels halt their assault, and urged Bozize's government to ensure the safety of civilians.