TEHRAN — The authorities on Monday ordered the immediate evacuation of flood-stricken cities in western Iran as rivers burst banks, dams overflowed and vast areas were cut off from communication.

The highest level of alert was declared in Lorestan Province with four or five cities “completely critical,” state television reported from Khorramabad, the provincial capital.

“In Khorramabad the water has risen by as much as three meters in parts,” the television broadcast said, with reports elsewhere of areas “completely submerged with residents stranded on their rooftops.”

The Red Crescent’s provincial director, Sarem Rezaee, said his organization had lost contact with much of the region.