ATHENS: At least seven people died on Wednesday and more were missing after a strong overnight downpour flooded three towns in Greece, officials said.

The flooding struck the towns of Mandra, Nea Peramos and Megara, a semi-rural area west of Athens where many warehouses are located.

"Everything is lost, the disaster is biblical," Mandra mayor Ioanna Kriekouki told state TV ERT.

"We have people who are trapped... we need machinery to get them out of their homes," said Kriekouki, who was also immobilised in her home.

Five people were found inside and outside their homes, the fire department said. Another two bodies were found in the coastal areas of Aspropyrgos and Elefsina, the coastguard said.

State TV ERT said at least three more people were missing.

Prime Minister Alexis Tsipras said the deaths had been caused by "disastrous flood" and expressed deep sorrow.

TV images showed large vehicles such as tanker trucks, buses and lorries nearly completely submerged in the muddy torrent.

The fire service said it had received over 300 calls for help and dispatched over 120 firemen to the area.