Fierce fighting has broken out in the town of Bunia in the north-east of the Democratic Republic of Congo, just 24 hours after the arrival of an advance party of French peacekeepers.
The French are leading an EU force to bolster peacekeeping efforts
The sound of gunfire and mortar shells preceded an unpredictable battle in the centre of the city, says the BBC's Ishbel Matheson, who is in the United Nations compound in Bunia.
Wild gunfire ricocheted off buildings and civilians ran for cover.
After four hours the Lendu militia trying to secure positions in town were driven back.
And heavily-armed French troops drove into town from their airport base to face a tense stand-off with the Hema militia, controlling the town.
Reports of casualties remain sketchy - but the AP news agency quoted an unnamed aid worker who said the bodies of four civilians had been recovered.
Both groups are said to be vying for control before the full deployment of the international force.
Despite the violence, French troops were proceeding with their deployment.
"The fighting in Bunia today does not change anything," French army Colonel Denis Koehl told a news conference.
"We expect to send troops into Bunia in the middle of next week."
French soldiers form the nucleus of a 1,400-strong UN-mandated force to provide security in Bunia, where hundreds of people have been killed during weeks of violence between rival ethnic militias.
Our correspondent says that, although some of the mission has arrived in Bunia, the bulk of it has not, and there is not much that peacekeeping soldiers can do at the moment.
And the people who so rapturously welcomed the French yesterday are now asking if anything has changed, our correspondent says.
The European Union ratified the dispatch of the force on Thursday - the first time EU peacekeeping troops have been deployed outside Europe.
France, which is experienced in intervening in African trouble spots, will supply about 700 of the troops.
As well as the UK, diplomats say Belgium, Sweden and Ireland may also participate, along with a number of African nations such as South Africa and Senegal.
Residents were relieved to see the French troops arrive on Friday
The Congolese Government has denied that its troops were involved in killings in Ituri over the weekend, in which fighters from the majority Lendu community are reported to have slaughtered at least 100 people in a village populated by Hema people.
Tens of thousands of refugees, many of them children, have been fleeing attacks from militia around Bunia, according to Ugandan reports.
Civilians have been arriving in the Congolese town of Beni, 150 kilometres (93 miles) to the south, and their numbers have raised concern about a possible food crisis there.