A barricade that symbolized the angry refusal of ethnic Serbs in northern Kosovo to merge with the rest of the country was removed on Wednesday after three years.

A bulldozer was brought in to shift the large pile of earth and concrete blocks that lay on the main bridge over the Ibar river in the northern flashpoint town of Mitrovica, an AFP correspondent reported.

Russian Foreign Minister Sergei Lavrov on Tuesday urged the OSCE to put pressure on Ukraine to implement a roadmap for de-escalating the violence drawn up by the pan-European security body.

"Ukrainian leaders absolutely refuse to implement the (de-escalation) roadmap and we call all countries members of the Organization for Security and Cooperation in Europe to put pressure on Ukrainian leaders," Lavrov told reporters in the Serbian capital.

The death toll from devastating floods and landslides that hit Serbia earlier this month has risen to 51, Prime Minister Aleksandar Vucic said Thursday.

Among those killed was one fireman, Vucic told the Serbian parliament, as he read out the names of the victims.

Forsenic experts in Serbia have uncovered the remains of ethnic Albanians killed during the Kosovo war in a suspected mass grave, officials said Tuesday.

Since the exhumation began at the Rudnica quarry near the southwestern town of Raska in April, "the remains of 21 persons have been found," Serbia's commission for missing persons said in a statement.

The death toll from cataclysmic floods in the Balkans rose by six to 57 on Friday as people returned home to salvage what belongings they could in a huge clean-up operation.

The task facing the thousands of rescue workers, volunteers and soldiers was immense, with dozens of towns and villages devastated by the region's worst natural disaster in living memory.

Floodwaters crept lower in the Balkans Thursday after the region's deadliest natural disaster in living memory, revealing widespread devastation as governments sought outside aid and warned of major damage to their economies.

As thousands of relief workers began an immense clean-up operation, the first of some 150,000 people evacuated over the past week were allowed to return to their towns and villages to pick up the pieces.

A landmine dislodged by devastating floods in the Balkans exploded in Bosnia, officials said Wednesday, hurting no one but highlighting the dangers of a huge clean-up operation as governments began counting the costs.

The device, one of an estimated 120,000 mines left over from the 1990s Yugoslav wars, went off overnight in the Brcko district of northern Bosnia, the national Mine Action Center (MAC) said.

Serbia declared three days of national mourning Tuesday as the death toll from the worst floods to hit the Balkans in living memory rose to 49 and health officials warned of a possible epidemic.

More than 1.6 million people have been hit as the river Sava and its tributaries have burst their banks, inundating tens of thousands of hectares of farmland and destroying homes and buildings.

The United States is sending 26 tons of humanitarian aid to the Balkans to help with relief efforts after floods devastated the region, the Pentagon said Monday.

The assistance included water purification units, water cans, generators, fuel, kitchen equipment, sleeping bags, shovels and wet weather gear, a Pentagon spokesman, Lieutenant Colonel Cathy Wilkinson, said.

Bosnia said Monday it was witnessing "the biggest exodus" since the 1990s war after the worst floods in a century inundated huge swathes of the Balkans, killing at least 47 people.

Muddy waters from the Sava River have submerged houses, churches, mosques and roads in Bosnia, Serbia and Croatia after record rainfall last week wreaked havoc across the region.