All injured persons, including a member of the international peace mission in Kosovo, were hospitalised and none of them are in critical condition.
Eye-witnesses said that a person came up to the entrance of the bar and threw in a hand grenade.
"This is a disaster, I am very worried, the man came walking peacefully and threw in the bomb. It could have been done by anyone and it happened at a time when a lot of young people were around here," the head of the Serb List for Kosovo, Oliver Ivanovic, told the media. Ivanovic, who was in the bar at the time of the attack, said that he was worried about the lukewarm response of the Kosovo Police Service and the Kosovo Force (KFOR).
Members of the UN Mission in Kosovo (UNMIK) blocked the entrance to the bar, located in the vicinity of a bridge over the River Ibar. An investigation was under way.
Local Serbs rallied and went on a protest march towards the bridge which divides the town into its northern and southern parts.
Sources from the northern Kosovska Mitrovica said that a 16-year-old Albanian from the southern part of the town was arrested on suspicion of attacking the bar.
The spokesman for the Kosovo police service, Veton Elshani, told the media in Pristina that one person was arrested, but he would not reveal the person's identity.
The Kosovo government strongly condemned the attack, stating that cooperation between the public and police was needed more than ever to identify and bring to justice the perpetrators. The government called on the public to keep calm and not to give in to provocation.
A member of the Belgrade negotiating team in talks on Kosovo's status, Marko Jaksic, said that he would urge handing the attacker over to the Serbian police and judiciary. Jaksic believes that the UNMIK is inefficient.
"We will ask that the main bridge over the Ibar be closed until Kosovo's status is defined. Residents have organised themselves and will start keeping watch on the bridge as of tonight," Jaksic said.
Serbian Prime Minister Vojislav Kostunica said that responsibility for the attack rested "with Albanian terrorists and international representatives, who with their acts or failure to act are encouraging them".
"Albanian separatists have responded promptly to (international mediator Martti) Ahtisaari's statement that Serbs are guilty as a nation by throwing a bomb at innocent Serb residents in Kosovska Mitrovica," Kostunica was quoted by Beta news agency as saying.
Serbian President Boris Tadic strongly condemned the attack, describing it as a terrorist act, and called on the international community to respond promptly and punish the perpetrators, Beta reported.
Tadic spoke with UNMIK representative Steven Schook on the phone and Schook assured him that KFOR and UNMIK would take all necessary measures of protection and keep him updated on the situation.