* Serbs in northern Kosovo refuse to recognise Pristina
* Dispute over border crossings sink talks in Brussels
* NATO says it will use force again if troops are attacked (Adds fresh quotes from NATO)
By Branislav Krstic and Fatos Bytyci
MITROVICA/PRISTINA, Kosovo, Sept 27 (Reuters) - At least 16 Kosovo Serbs and four NATO troops were injured in clashes at a disputed Kosovo-Serbian border crossing on Tuesday, NATO officials and local authorities said.
Witnesses said troops from the NATO peacekeeping force KFOR responded with fire arms, teargas and rubber bullets to disperse a crowd rallying against the removal of a Serb-held barricade on a small road about 150 meters from the Jarinje border post.
NATO spokesman Ralph Adametz said the incidents started when Serb protesters drove a vehicle at NATO troops and a soldier was injured.
"During the incident an attempt was made to seize the soldier's weapon and after a verbal warning a KFOR soldier fired a shot injuring the civilian attempting to steal the weapon.
"A number of pipe bombs were thrown at the KFOR personnel causing minor injuries."
Adametz said that shots were fired at NATO troops from the vicinity but he gave no details about how other protesters were injured at the border post 100 kilometers (60 miles) north of Pristina.
Milan Jakovljevic, the head of the hospital in the Serb, northern part of Mitrovica, a tense city divided into Albanian and Serb districts, said six patients had serious gunshot wounds and not injuries caused by rubber bullets.
Jakovljevic also said about ten other protesters from Jarinje sought medical attention for minor injuries.
The clashes in Jarinje prompted Belgrade to cancel talks with Pristina in Brussels under EU auspices aimed at mending daily ties such as flow of people and goods, property rights and personal documents.
"The talks will not resume until we see what will happen at the two border crossings. We need to resolve that situation in talks with the international community," Borislav Stefanovic, Serbia's chief negotiator said in a TV broadcast. "There are no other issues for us but this one."
The Pristina government wants to reinstate its presence in the largely lawless northern area which pledges its allegiance to Belgrade, three years after Kosovo -- which has an Albanian majority -- declared independence from Serbia.
Serbia, which opposes Kosovo's independence, has warned that taking over the contested posts could lead to more clashes.
In a statement, Serbia's President Boris Tadic called on Kosovo Serbs to remain calm and urged KFOR to show restraint.
"International peacekeepers are there to defend unarmed people, not to clash with them," Tadic said. "No problem can be solved through violence and jeopardising lives will not contribute to the defence of our (national) interests."
"WE ARE SOLDIERS ONLY"
In northern Mitrovica, angry Serbs damaged two police vehicles. NATO and police brought reinforcements to the southern, Albanian part of the city, a Reuters eyewitness said.
In Pristina, Kosovo deputy prime minister Hajredin Kuci said authorities will maintain efforts to unblock roads in Kosovo's north. "We will face criminal structures and ... always protect citizens," he said.
NATO has called on Kosovo and Serbia to find a peaceful resolution to the issue but warned protesters at the roadblocks that it will act with force if soldiers' lives were at risk.
"We are not political guys, we are soldiers only, and if we get some threat from outside we will act like soldiers," Adametz said.
On Sept. 16, Pristina sent police and customs officials to two northern crossings, Brnjak and Jarinje, previously staffed mostly by ethnic Serbs.
In response, Kosovo Serbs blocked all the key roads leading to the border posts and built a separate dirt track near Jarinje to bypass the crossing into Serbia.
In July when Pristina tried to install customs at the two crossings to enforce a trade embargo with Serbia, armed local Serbs drove Kosovo police back and burned the Jarinje border post. One ethnic Albanian policeman died.
Earlier on Tuesday, KFOR troops used bulldozers to remove the roadblock near the Jarinje border post and briefly detained five local Serbs.
Kosovo, a new state of about 1.7 million mostly ethnic Albanians, has been recognised by more than 80 countries, including the United States and most of the EU, since 2008.
But northern Kosovo, a predominantly Serb region with a population of about 60,000, has so far refused to recognise Pristina as its capital and pledges allegiance to Serbia. The remainder of Kosovo's 120,000 Serbs are living in enclaves in Kosovo proper.
Serbia cherishes Kosovo as its historic heartland and most of its medieval monasteries and churches are there. It lost control over Kosovo in 1999, when a NATO bombing campaign halted a Serb counter-insurgency war against ethnic Albanian rebels.
Belgrade is under pressure to mend ties with Kosovo to gain EU candidate status. But the Kosovo issue will be an important factor in Serbia's parliamentary election due next year. (Additional reporting and writing by Aleksandar Vasovic, Editing by Rosalind Russell)