Authorities have spent two decades trying to unearth the 1 million land mines planted during Bosnia’s 1992-95 war. Before the floods, nearly 120,000 remained in 9,416 marked minefields.

Then floods washed away river banks and fuelled landslides that have unearthed minefield warning signs and, in many cases, the unexploded booby traps themselves.

An official at Bosnia’s Mine Action Centre, Sasa Obradovic, said his agency would deploy mine-hunting scouts starting Monday.

“Mines have surfaced now in areas where they have never been,” he said.

The unearthing of mines in Bosnia could create an international problem as flood waters carry the weapons downstream. Bosnia’s tributaries feed the Sava River, which runs along the Croatia border and meets the Danube in Serbia. The Danube then flows through Bulgaria and Romania into the Black Sea.

Experts warn that mines could travel through half of southeast Europe or get stuck in the turbines of a hydroelectric dam.

“We will work with Croatia and Serbia on the problem,” Mr. Obradovic said.

Under an international treaty, Bosnia was supposed to be mine-free by March 2009, but that deadline proved impossible to meet. Europe’s most mine-infested nation received a new deadline of 2019 to clear remaining mines and other unexploded ordnance.

Authorities say that, before the flooding, hidden mines threatened 2.4 per cent of Bosnian territory and more than half a million nearby residents.

Since the war’s end, Mr. Obradovic said mines in Bosnia have killed at least 601 people and wounded 1,121. He said four people have been killed and eight wounded already this year.