|Police said that they were "forced to react" after objects were thrown at them by demonstrators [Reuters]
Police in Kosovo have fired tear gas and a water cannon at hundreds of Kosovo Albanian protesters who tried to blockade the border with Serbia, arresting 146 demonstrators.
At least 52 people, including 31 police officers, were injured in clashes on Saturday at two border crossings, police said in a statement.
They said they were "forced to react" after being pelted with stones and metal objects by members of the Kosovo Albanian Self-Determination movement, which opposes any contact with Serbia.
The group, led by hardline opposition leader Albin Kurti, had announced plans to temporarily block the border in order to bar Serb products from entering the breakaway territory.
Kurti joined protesters waving Albanian flags, saying: "Serbia is an enemy country for Kosovo, that is why our motto is 'Serbia will not pass through'."
After an hours-long confrontation, police managed to disperse the protest and restore traffic on the road leading from the border to the capital city, Pristina, allowing two trucks from Serbia across under police escort.
Police had earlier cordoned off the road outside the northern town of Podujevo, some six kilometres from the border with Serbia, to prevent the movement from blocking two border posts.
In an initial clash, security forces pushed the crowd back with batons and pepper spray.
Later in the day police and protesters also clashed near another border post, Konculj, some 70km east of Pristina.
The government in Pristina denounced the blockade, and Hashim Thaci, Kosovo's prime minister, has said his government would do its best to prevent it.
In a statement released after the protest, the Kosovo government urged the leaders of Self-Determination "to restrain from the use of violence and attempts to block the freedom of movement guaranteed by the constitution".
At a post along the Albanian border, Kosovo police earlier stopped several busloads of Albanians on their way to join the protest, a police spokesperson told reporters in Pristina.
But, according to local media in Tirana, dozens of protesters nevertheless managed to break through and take part in the demonstration.
Belgrade and Pristina have been at loggerheads over bilateral trade ever since Kosovo, which has an ethnic Albanian majority, unilaterally proclaimed independence from Serbia in 2008.
However in September, after months of EU-mediated negotiations, the two sides agreed to implement a free trade agreement.
Neither Kosovo's minority Serbs nor Belgrade recognise Pristina's 2008 declaration of independence, accepted by most of the European Union and many other countries, considering Kosovo still to be a province of Serbia.