Emergency crews scrambled to bolster the banks of the Tisza River that flows into Serbia from Hungary after it reached its highest level in parts of the two countries already hit by flooding of the Danube.
Further downstream in Romania, the rising Danube forced authorities to evacuate more than 4,700 people, mainly in the southern towns of Calarasi and Fetesti.
In neighbouring Bulgaria, thousands of volunteers joined army troops to strengthen embankments along the surging Danube with sandbags.
The situation was expected to worsen across the Balkans within hours, with heavy rainfall forecast later today or tomorrow, adding to the melting snow which has contributed to the flooding.
The Tisza River rose to 980 centimetres in the Hungarian town of Szeged, surpassing the 1970 record by 20 centimetres, and was moving south towards the already bursting Danube, which flows on through Serbia, Romania and Bulgaria.
“About 158,000 people in 51,150 homes are threatened by the Tisza,” said Tibor Dobson, spokesman for Hungary’s national disaster prevention agency.
“High water is threatening 254 communes, 523 people have been evacuated and over 600 are working on reinforcing dykes in the town of Szeged,” he added.
Downstream on the Serbian side of the border, where the river is known as the Tisa, the floodwaters had already reached the highest recorded level of 920 centimetres near the town of Novi Knezevac.
As the work on the dykes intensified in Bulgaria, the government there came under increasing pressure over its handling of the disaster, facing a parliamentary no-confidence motion that is likely to fail.
“The major threat does not come from overflowing but from a breakthrough in the anti-flood defences that have survived continuous high water pressure for a month now,” a Bulgarian expert said.
Three other Danube tributaries, the Vit, Iskar and Osam rivers, burst their banks yesterday as high water levels caused them to flow backwards, said Bulgaria’s Deputy Farming Minister Byurhan Abazov.
About 2,000 volunteers had filled more than 90,000 sandbags to cork breaks in dykes, the civil protection agency said, as water levels at the far northwestern Bulgarian town of Vidin struck 971 centimetres.
Before the latest threat from the Tisa, officials in Serbia had already estimated that the flooding of the fertile plains north of Belgrade would have a heavy financial impact on the country’s crucial agricultural sector.
About 220,000 hectares of farmland has been submerged in the northern province of Vojvodina, considered Serbia’s breadbasket.