The first extra contingent of 750 soldiers being sent by the UK arrived in the region's capital Pristina overnight.
UN staff were pulled out of the flashpoint town of Mitrovica on Thursday. Serbia has accused both the UN and Nato of failing to protect Kosovo's Serbs.
Nato troops has been trying their best to hunt for the sniper. French forces searched black of flats near the river Ibar early in pursuit of gunmen after reports of attacks overnight.
Nato troops in Mitrovica shot and killed a ethnic Albanian sniper who fired at peacekeepers. The sniper was found in a block of flats in the northern half of the town, as reported by Lieutenant Colonel Jim Moran.
A further 600 peacekeepers were being sent to join German forces in Kosovo, with deployment starting on Saturday, said Germany's Defence Minister Peter Struck on Friday.
France also says it is sending about 400 more troops immediately. Denmark has pledged 100 more.
Now, about 18,500 peacekeepers are already based in Kosovo.
UN Secretary General Kofi Annan said it showed that communities in Kosovo were not ready to accept multi-ethnicity.
However, in Serbia itself, thousands of people demonstrated peacefully in central Belgrade on Friday following a government call to show solidarity with Serbs living in Kosovo.
Carrying Serbian flags, pictures of Kosovo monasteries and religious icons, the crowds chanted "We're not giving Kosovo away" and "Kosovo is Serbia".
"The situation is calm but very volatile, very fragile and could escalate any minute," one French officer told the Associated Press.