Bangui - Rebel fighters captured the southern city of Bangassou in the Central African Republic on Sunday, weeks after they were accused of an attempted coup and ahead of partial results from a tense presidential election.
A coalition of armed rebel groups, which control two thirds of the coup-prone country, launched an offensive on December 19 aiming to disrupt last weekend's elections and "march on Bangui".
They have been kept away from the capital so far by federal soldiers, UN peacekeepers and reinforcements sent from Russia and Rwanda.
But the rebels attacked Bangassou, which sits on the border with the Democratic Republic of Congo about 750 kilometres (470 miles) from Bangui, at dawn on Saturday.
"The rebels control the town," Rosevel Pierre Louis, head of the UN peacekeeping force MINUSCA's regional office in the city, told AFP. "They are everywhere."
Government troops had "abandoned their position and are at our base", he added.
Doctors Without Borders (MSF) said it had transported 15 wounded in the fighting.
MINUSCA tweeted that UN peacekeepers had been protecting the city and that the bodies of five fighters had been found.
It added that the fighters attacking the city were allied to former president Francois Bozize.
The government of President Faustin Archange Touadera -- the favourite to win December 27's election -- has accused Bozize of fomenting an attempted coup, a charge he has denied.
The rebels also waged a dawn assault Saturday on the town of Damara, which is Touadera's stronghold around 70 kilometres (45 miles) north of Bangui, but were repelled by troops, MINUSCA said.
Roland Marchal, a specialist on the Central African Republic at France's Sciences Po University, said "the rebels thought they could reach Bangui, but they did not expect the arrival of the Russians and Rwandans".
Analyst Nathalia Dukhan said the rebels have adopted "a long-term strategy by securing the resources to suffocate Bangui".
The landlocked country is one of the poorest in the world and among the most volatile, suffering coups and wars since independence from France in 1960.
In 2013, it spiralled once more into bloodshed when then-president Bozize, who had himself seized power in a coup a decade earlier, was ousted by a mainly Muslim coalition called the Seleka.
Bangassou resident Ismail said Sunday's attack had been expected locally for around two weeks, and many had fled over the border to DR Congo.
"My children left, I stayed with my wife," Ismail told AFP as gunshots could be heard over the phone.
The UN force was not yet able to provide details on the number of dead and wounded in either the Bangassou or Damara attacks.
Bangassou has previously been the target of brutal assaults.
In 2017, "anti-balaka" militiamen, drawn mainly from Christian communities, attacked the city, slaughtering dozens of Muslim civilians as well as 12 UN peacekeepers.
Touadera said in a speech on December 31 that his country "is at war".
"Its survival is threatened. We are going to win this asymmetrical war".
The capture of Bangassou comes on the eve of partial results being published for the presidential election.
Lack of security meant that voting did not take place in 29 of the country's 71 sub-prefectures, while thousands were prevented from casting ballots or never received their voting cards.
This week Touadera's party claimed victory, while a coalition of opposition groups called for the election to be annulled, claiming ballot stuffing and electoral rigging.
MINUSCA spokesman Vladimir Monteiro accused the opposition of making "false and baseless" allegations.
"Bizarrely, they don't say anything about former president Francois Bozize, an ally of the armed groups who are responsible for the current violence," he tweeted.
On Sunday the UN mission said in a statement that the main armed groups "the UPC, the MPC, the 3R, the FPRC, the anti-balakas and former president Francois Bozize are responsible for these attacks and the grave consequences for the civilian population".
The definitive results from the first round are not expected before January 18, and if there is no outright winner a runoff will be held on February 14.