Heavy rains caused floods that killed 21 people in Romania and thousands of others were evacuated from their homes on Tuesday as rivers threatened to burst their banks.

People climbed trees to escape the rising water and many houses, roads and railway lines were destroyed or damaged by the floods, officials said.

Hundreds of police and emergency workers were deployed to the rescue operation while several localities along the Danube River took urgent measures to stop it from breaching its banks.

"The situation is tragic, the damage is of a scale hard to imagine," Gheorghe Flutur, president of Suceava department, one of the worst hit regions, told Mediafax news agency.

Twenty-one people have been confirmed dead and at least one other was missing since the floods started last week, emergency inspectorate spokesman Alin Maghiar told AFP.

Nineteen died after being carried away by high waters and two others were killed by lightning, he said.

Most of the deaths occurred on Monday night in two departments close from the Ukrainian border.

In the northeastern town of Dorohoi, six people died in overnight Monday to Tuesday, according to officials. More than 1,700 people had to be evacuated and some scrambled up trees to avoid the water, witnesses said.

Flooding receded on Tuesday afternoon but houses were badly damaged by the water, which rose above one metre (3.3 feet) in some places. Roads into Dorohoi remained under water.

Heavy rain has fallen for much of the past week in the Balkan country and forecasters have warned that it will continue in northeastern Romania until Wednesday morning.

Several old people died last week in the central regions of the country after being carried away by high waters.

On Tuesday night, authorities in northeastern Neamt department ordered the evacuation of about 11,000 people along the river Siret, a Danube tributary threatening to overflow.

In the northern Suceava, hundreds of people were evacuated Tuesday for the same reason.

"Ten villages have been evacuated. 1,870 people will spend the night in monasteries, schools, cultural centres or with relatives," a spokeswoman for the Suceava authorities told AFP.

About 1,100 sheep were moved to higher ground in the mainly rural region.

Further along the Siret, in Sendreni, inhabitants and emergency servicemen reinforced dykes with bags of sand to prevent floods.

Prime Minister Emil Boc flew to the affected zones in northeastern Romania and said Bucharest could ask for help from an emergency European fund.

Damages could amount to more than 0.6 percent of gross domestic product, Interior Minister Vasile Blaga said.