About 6,200 people have been forced to flee their homes in southern Romania so far this week, and another 8,000 were being readied for evacuation as the situation deteriorated.
Hundreds of police and soldiers were engaged in the emergency operation, racing against time to secure the bulging banks of the Danube as the water level began to peak after converging from central and southeastern Europe.
Floodwater levels have broken 100-year records in several rivers across the Balkans this week, but the region has shown better preparedness to deal with the problem of melting snows, so far preventing any loss of human lives.
One such measure was the recent decision by Romanian authorities to deliberately flood thousands of hectares (acres) of farmland and forests in a bid to protect inhabited southern districts.
The man-made embankments near the southern village of Bistret, in one of the worst-hit areas, were in danger of bursting under pressure because heavy rainfall topping up the already rising waters.
According to an assessment by Romania's interior ministry, about 120 localities were affected by floods, 170 houses were destroyed and nearly 700 others damaged.
Farmland under water
More than 20,000 hectares of farmland and another 17,000 hectares of forests and other land were under water, along with some 500 kilometres of roads.
Meanwhile, a swollen Danube tributary in Hungary topped the 10 metre-mark a day after breaching its record level, and remained a threat to at least 165,000 people and 52,000 homes in 306 localities.
Hungarian authorities said more than 18,000 people, including the army, civil defence, firefighters and volunteers, were fighting to contain the Tisa River, which in Serbia joins the Danube that flows on through Romania and Bulgaria.
Officials in Serbia said the bulging Danube had stabilised, but that thefloodwaters had risen to 935 centimetres on the Tisa.
The army joined emergency civil teams to strengthen sandbagged dykes along the most critical part of the Tisa between Novi Knezevac and Senta, amid heavy morning rain that is forecast to continue for the next few days.
Emergency crews are hastily working to strengthen sand embankments that have been built to spare the towns of Gradiste and Golubac, on the border with Romania.
The Danube is expected to reach a new peak later in Bulgaria, where the town of Nikopol was partly flooded and some riverside houses were evacuated.