Chadian troops entered the neighbouring Central African Republic (CAR) on Tuesday following an appeal from Bangui\'s President Francois Bozize after rebels seized a number of key towns, a CAR military official said. A coalition of three rebel factions is threatening to overthrow the Bozize government, demanding respect for different peace accords signed between 2007 and 2011. \"Heavily armed elements of Chadian ground forces aboard 20 vehicles arrived in the middle of the afternoon at Kaga Bandoro where they joined elements of the Central African armed forces based there,\" the CAR official told AFP. The intervention occurred after the rebels captured the diamond-mining and garrison town of Bria, 400 kilometres (250 miles) northeast of the capital. Chadian President Idriss Deby Itno is a close ally of Bozize whom he helped when the high-ranking army officer seized power in 2003. Chadian forces, who have successfully quelled rebellions in the east of their own country, had already been sent to CAR in November 2010 to drive out Convention of Patriots for Justice and Peace (CPJP) rebels from the northeastern town of Birao. The military official said Chadian forces were to \"back up Central African armed forces in the counter-attack aimed at retaking towns that have fallen into the hands of the rebels\". Bozize was expected in Kaga Bandoro on Tuesday night before the allied troops would head for the \"occupied areas\", he added. A coalition of rebel factions operating under the name of Seleka CPSK-CPJP-UFDR earlier Tuesday took Bria, ousted the underpaid, disorganised and badly equipped government forces and began looting its shops. The attack came eight days after a UFDR fringe group attacked the towns of Ndele, Sam Ouandja and Ouadda. These attacks and the condition of his notoriously weak armed forces prompted Bozize to seek outside help. Seleka, or Alliance, the coalition of three rebel groups, demands that a string of peace agreements signed between 2007 and 2011 which arrange for the fighters\' disarmament and reintegration into society be respected. In a statement sent to AFP on Monday, Seleka said that unless Bozize\'s administration agreed to discuss their grievances, the insurgents would do all they could \"to change, sooner or later, this predatory regime\". The rebels\' attacks in the north in recent days have left at least 14 soldiers dead. In Tuesday\'s attack on Bria rebels \"entered the town and began looting shops\", a senior military official told AFP on condition of anonymity, adding that some local residents had taken advantage of the chaos and joined in the pillaging. The Central African armed forces \"opened fire on the rebels who were trying to get in, but (the troops) were later forced to fall back\", the official said. Another military official earlier said that soldiers at Bria\'s army base had \"tried to resist but then quickly many retreated and the base fell to the assailants\". Bria is the main town in the poor, landlocked country\'s diamond-mining area. According to government figures, Bria, population 30,000, accounts for 10 to 15 percent of the roughly $65 million (50 million euros) in diamonds the Central African Republic produces each year. Resident Christelle Padoundji, 28, told AFP by phone \"the rebels are now in control of the town.\" The fall of Bria comes after a series of attacks on four northern and central towns in the country, which has been rocked by rebellions and coups for more than 30 years. Rebel forces travelled about 300 kilometres (200 miles) to capture Bria after claiming control Sunday of the northern town of Ndele, which lies near the Chadian border on a major trade route between Cameroon and Sudan. On Monday, the army said it had lost contact with 40 soldiers who were ambushed near Ndele. The Seleka coalition was formed in August by dissident factions from two rebel groups that had signed peace deals with the government, together with a third group that has not signed any deal with Bangui. President Bozize has been re-elected twice -- in 2005 and 2011 -- since seizing power. But he has had trouble consolidating his rule over the strife-torn country. \"Bozize only governs Bangui and the south,\" a Western diplomat recently commented. Describing the rebel attacks, academic Isidore Mbamo told AFP: \"This is in reality an insurrection that is progressively taking shape and which is far from stopping.\" A senior military officer said on condition of anonymity that the latest rebellion could spell the end of Bozize\'s regime. \"Once it starts, only a foreign intervention can save the regime,\" he said. The Central African Republic has been rocked by rebellions and coups since the fall in 1979 of military dictator Jean-Bedel Bokassa, who for almost three years reigned as emperor. The instability has hobbled progress in a country that ranks among the world\'s poorest despite a wealth of raw materials such as uranium, diamonds and timber.