Two people were killed in fighting in the capital of Central African Republic and six peacekeepers from Burundi and Cameroon were wounded in an ambush, a spokeswoman for the United Nations mission in the country said on Saturday.

The violence follows days of fighting that threatens the interim government of President Catherine Samba-Panza, who took office in January aiming to end two years of unrest in which thousands have died and more than 1 million have fled.

Samba-Panza said she would not step down in the face of heightened political pressure and there were signs late on Saturday that tensions could be easing as one militia group withdrew its call for her resignation.

"I will not resign. I must lead this country until the end of my mission," Samba-Panza told state radio.

The unrest is a struggle for power and resources in an impoverished country with reserves of gold and diamonds. Rival communities have also clashed across religious lines.

Those killed overnight include a gendarme and a local leader for a militia known as "anti-balaka", whose adherents follow Christianity and animism.

The peacekeepers were attacked in a neighbourhood near the Bangui airport and two were seriously hurt, Myriam Dessables, a spokeswoman for the country's UN mission MINUSCA, told Reuters.

The United Nations took over peacekeeping in mid-September from a mission run by the African Union. The country was plunged into chaos as mostly Muslim rebels from a coalition called the "Seleka" seized power in March 2013.

Its rule was marked by abuses that prompted a backlash from the "anti-balaka". France sent troops to its former colony and an existing African peacekeeping force was beefed up.

Sporadic violence has continued despite the Seleka leader's resignation from the presidency in January.

A Reuters witness said there was little gunfire in the capital on Saturday after days of violence rated the worst in months. Dessables said some airline companies had cancelled flights to Bangui for security reasons.

"ARRESTED IN ERROR"

On Saturday, the Seleka called on Samba-Panza to quit on the grounds that she asked it to leave Bambari, its stronghold town in the centre of the country. The demand amounted to a threat to its citizenship.

Most Muslims have fled the south of the country due to violence against them. This has created a de facto partition, which some members of Seleka leaders have pushed to formalise.

Anti-balaka ministers in Samba-Panza's government also quit this week but on Saturday the militia group withdrew its call for the president's resignation after a meeting with her.

"We agreed to put in place a working contact group to reflect on the best way for us to unblock this crisis. We are no longer demanding her resignation," Alfred le Grand Ngaya, an anti-balaka political adviser, told Reuters.

Samba-Panza agreed to free their arrested militants, he said. In return, the militia asked its members to take down barricades and allow people to go back to work, he said.

A spokeswoman for Samba-Panza confirmed the meeting and said the president is open for dialogue.

"Perhaps people were arrested in error and it's not impossible to liberate them but it's up to the judicial authorities," said spokeswoman Antoinette Montaigne.

In a fresh sign that the crisis may be easing, a taxi drivers union told national radio it would end its strike if security was restored and other conditions were met.

Civil society groups issued a statement on Saturday that blamed militias for violence and called for national dialogue.