The flood situation in Orissa further worsened on Tuesday with the toll mounting to 17.

"The situation is grave," Chief Secretary Pratip Kumar Mohanty said while indicating that both the upper and lower catchments of Mahanadi River are receiving heavy precipitation.

If the rain continues, the situation will deteriorate further, but the administration is geared to meet any eventuality, he said.

The floods in the Mahanadi system have already affected over three million people in six coastal districts while inhabitants of 901 villages are marooned.

Army and naval personnel are conducting rescue and relief operations in the worst-hit areas.

Close to 4,000 villages in 87 blocks in 16 districts have been affected in the floods, official sources said.

The meteorological department said heavy to very heavy rainfall has occurred at isolated places over the upper catchment of the Brahmani, a turbulent river that periodically causes floods in the coastal plains.

Rainfall has also occurred over the catchment areas of Baitarani, Subarnarekha and Budhabalanga rivers, the sources said.