Sixteen people were killed in two days of clashes between Fulani herdsmen and the mainly Muslim Seleka militia in northern Central African Republic, a police source told AFP on Tuesday.

"According to an initial toll, 16 people, most of them armed Fulani herdsmen, were killed and more than 20 others were wounded in the clashes," said police officer in the northern town of Kaga Bandoro who asked to remain anonymous.

The clashes began on Sunday and were not connected with a separate wave of violence in the capital, Bangui, on Monday in which three people were killed.

Police taken hostage

Three people died of gunshot wounds in fighting in the capital of Central African Republic on Monday as the sound of fire from machine guns and heavier weapons resounded across Bangui, witnesses and medical authorities said.

Heavily armed members of the former rebel group Seleka took six police officers hostage in Bangui on Sunday, Jean Serge Bokassa, the minister of territorial administration and public security, told Reuters.

It was not clear if the shooting and kidnapping were linked. The gunfire died down as night fell, witnesses said.

"We demand the liberation of the officers who were taken hostage ... The government will do everything possible to free them," Bokassa said.

Insecurity has persisted in the months since President Faustin-Archange Touadéra was sworn in in March, after winning an election intended to draw a line under inter-communal and inter-religious violence that involved the mainly Muslim Seleka and began in 2013.

MSF strike

Medical aid charity Medecins Sans Frontieres (MSF) will suspend non-essential activity for three days, starting on Wednesday, to protest the killing of one of its drivers in an ambush, its country director said on Monday.

It is the group's second suspension of operations in the country in a little over a month after acts of violence.

Unidentified gunmen shot an MSF driver on Friday on the road between the towns of Sibut and Grimari northeast of Bangui. Last month, one of its drivers died in a similar incident.

"This (ambush) shows that humanitarian work is becoming more precarious in Central African Republic," head of mission Emmanuel Lampaert told a news conference in Bangui. "MSF wants its cry for help to be heard."

After the attack in May, MSF said it was forced to suspend activities until it could guarantee the safety of its staff. It resumed operations a day later.

-Reporting by Reuters and AFP