Nato is sending more troops to Kosovo where two days of clashes between Serbs and Albanians have left 22 people dead.
Nato has been scaling down its presence in Kosovo
About 1,000 new troops are being sent - 750 from the UK - to reinforce 18,500 K-For peacekeepers already there.
Hundreds of people have been injured in what is the worst ethnic violence in Kosovo since the 1999 war.
The trouble began in the divided city of Mitrovica on Wednesday, but has now spread throughout Kosovo with churches and Serb-owned houses set alight.
In the latest violence, a Serb Orthodox church was set on fire in Mitrovica and another in the town of Obilic, west of the capital, Pristina - where about 100 local Serbs had to be evacuated.
And south of Pristina, K-For troops used teargas against Albanian protesters seeking to march on the village of Caglavica for the second day.
By the evening, a crowd of Albanians was reportedly throwing grenades and trying to storm a church being protected by Finnish peacekeepers in the central Kosovo town of Lipljan.
There have been no reports of injuries on Thursday.
Nato officials insist that the alliance and the United Nations, which administers the province, are committed to quelling tensions.
"I don't believe there is a possibility of a war. We will do what is necessary to restore and uphold law and order," Nato spokesman Jamie Shea said.
But the top commander of the Nato-led force in Kosovo, which is known as K-For, has authorised the troops to use force if necessary.
The European Union has called on local leaders to rein in the violence - and the main Kosovo Albanian political parties have issued a statement urging their supporters to call off the protests. The UN Security Council is due to discuss the issue on Thursday.
Serbia has condemned both Nato and the UN for failing to protect the Serb minority in the province.
Prime Minister Vojislav Kostunica said the attacks were "planned in advance and coordinated... this was an attempted pogrom and ethnic cleansing" against Kosovo's Serbs.
He has called for a state of emergency to be imposed in Kosovo.
Protesters in Serbia have taken to the streets again to demonstrate their support for the Kosovo Serbs - after having stoned and burned mosques and other Islamic buildings on Wednesday.
KOSOVO: KEY DATES
24 Sept 1998: Nato issues ultimatum to Milosevic to stop crackdown on Kosovo Albanians
24 Mar 1999: Nato begins air strikes against Yugoslavia over Kosovo
10 June 1999: Air strikes suspended after Milosevic agrees to withdraw troops. UN approves peace plan for Kosovo, establishes K-for peace force
11 June 1999: Nato troops enter Kosovo
10 Dec 2003: UN unveils road map on conditions Kosovo must meet by mid-2005 for talks on final status
17 Mar 2004: Serbs and Albanians clash in the worst violence seen since 1999
Tensions resurfaced in the flashpoint town of Mitrovica in northern Kosovo on Tuesday when at least two Albanian children drowned, allegedly as they were trying to escape from Serbs who chased them with a dog.
The boys' deaths came a day after an 18-year-old Serb was wounded in a drive-by shooting in the village of Caglavica prompting clashes between Serbs and Nato-led peacekeepers.
Flights in and out of Kosovo have been suspended and internal boundaries with Serbia have been closed.