Rebels in the Central African Republic on Tuesday seized Bambari, the country's fourth-largest city, five days before nationwide elections, the local mayor, government and UN sources said.
"The town is under the control of armed groups," Bambari Mayor Abel Matchipata said, while a senior government official confirmed "they are in the town, we are waiting for reinforcements, which are on their way."
The attack follows the government's accusations at the weekend that former president Francois Bozize was seeking to mount a coup with armed groups ahead of upcoming elections.
At CAR's request, Russia and Rwanda have sent military personnel to support the troubled country.
Bambari is located 380 kilometres (240 miles) northeast of the capital Bangui.
The attack, which began at 10 a.m., triggered a two-hour gunfight with CAR troops and the United Nations' peacekeeping force MINUSCA, sources in NGOs and the UN said.
"There has been no violence towards local people, but they have ransacked the police station, the gendarmerie and people's houses," Matchipata said.
The sources said the rebels were led by an armed group called the Unity for Peace in Central Africa (UPC), one of the militias contesting the government in the runup to the December 27 polls.
On Saturday, the government accused three militias of advancing along key highways towards Bangui. MINUSCA said late Sunday that the advance was halted and in some places pushed back and the situation was "under control".
The CAR is one of the poorest and most unstable countries in the world, experiencing only rare moments of peace since it became independent from France in 1960.
The presidential and legislative elections have been gripped by tension between President Faustin-Archange Touadera and a mosaic of armed groups that sprang up after the country spiralled into conflict in 2012.
Touadera is front runner in the poll, but his government holds sway over only about a third of the country.
Russia on Tuesday said it had dispatched 300 military instructors to the CAR at Bangui's request "to train the military personnel of the national army" under an existing cooperation agreement.
It had previously deployed 175 military instructors to the CAR, according to official figures.
The Kremlin has led a diplomatic and financial offensive in the CAR since 2018 in return for concessions to Russian companies to exploit its mineral wealth.
Rwanda has also sent "several hundred men" under a bilateral agreement, the CAR government said on Monday.
The deployment was confirmed by Rwandan President Paul Kagame, although he did not give details on numbers.
Thousands of people in the landlocked country have died since 2012, and nearly a quarter of the population of 4.7 million have fled their homes.
The International Criminal Court's chief prosecutor, Fatou Bensouda, called for "calm and restraint" Tuesday ahead of the elections.
"Anyone who commits, orders, incites, encourages or contributes, in any other way, to the commission of crimes" would be liable for prosecution either by Bangui courts or by the ICC, Bensouda warned.
