NATO Secretary-General Jens Stoltenberg announced that the bloc would deploy an additional 700 troops in Kosovo amid ongoing tensions in the country's north.

The alliance will put a battalion from the reserve forces on heightened alert so it can also be deployed if needed, Stoltenberg told a news conference along with Norwegian Prime Minister Jonas Gahr Store on Tuesday.

His remarks came after at least 30 NATO soldiers were injured in clashes.

"We strongly condemn the unprovoked attacks against KFOR troops in northern Kosovo, which led to 30 peacekeepers being wounded. Such attacks are unacceptable and must stop," Stoltenberg said in Oslo.

"Violence sets back Kosovo and the entire region" and puts the Balkan countries' hopes of joining NATO "at risk," he said.

"Both Pristina and Belgrade must take concrete steps to de-escalate the situation, refrain from further irresponsible behavior and engage in the EU-facilitated dialogue, which is the only way to lasting peace," Stoltenberg said.

Kosovo's ethnic Serb minority boycotted local elections in the north in April, allowing ethnic Albanians to take control of the local councils despite a tiny turnout of less than 3.5%.

Eleven Italian and 19 Hungarian soldiers with the NATO peacekeeping mission in Kosovo (KFOR) sustained multiple injuries, including fractures and burns from improvised explosive incendiary devices.

Three Hungarian soldiers were also wounded by firearms, but their injuries are not life-threatening, KFOR said on Tuesday.

The injured personnel are currently under observation at a health facility.

Tensions have gripped Kosovo with protesters and security forces clashing in the northern Serb-dominated municipalities over the election of ethnic Albanian mayors. Albanians are the largest ethnic group in Kosovo, followed by Serbs, especially in the north, near the border with Serbia.

Meanwhile, more than 53 civilians were injured by shock bombs and tear gas, according to hospital sources.