Large stretches of property near rivers, tributaries and dams in the state with a population of 50 million were under water with more than 900 villages cut off by flooding, said provincial revenue minister Kaushik Patel on Saturday.
A damage estimate was not immediately available, but federal Home Minister Shivraj Patil announced a five billion rupee ($110 million) aid package for Gujarat after an aerial survey of the flood-affected areas on Friday.
"One hundred hours of rain in different parts of Gujarat has affected more than 70% of the state; 123 people died in various mishaps," state revenue minister Patel said.
In all, 4577 villages and 31 urban centres in Gujarat were hit by power cuts as rains pounded the state non-stop for four days, Patel said.
The 123 victims - including adults and children - died as they were washed away by strong currents after dams overflowed, while others were crushed when portions of buildings collapsed or were buried in mudslides, officials said.
At least 250,000 people have been evacuated because of heavy rains and flash floods in the state and the situation is likely to worsen with more rain forecast, federal Science and Technology Minister Kapil Sibal told reporters in New Delhi on Friday.
"We have to be prepared for the worst floods. Only after 4 or 5 July will there be a substantial fall in rainfall."
Public transport stalled
Train services were delayed as the floods damaged rail tracks while some had to be cancelled, marooning hundreds of passengers on railway platforms.
Shailendra Kumar, chief public relations officer for India's western railway, said about 400 passengers on a train stranded for almost 36 hours near Dakor, 100km from the commercial capital Ahmedabad, managed to reach makeshift shelter camps after wading through several feet of water early on Saturday.
Hundreds of vehicles have been
left stranded on roads
State authorities could not reach the train as the swirling waters made it impossible to reach the site and boats were not immediately available, he said.
The rains have also disrupted flights and left vehicles stranded on flooded highways, while all schools in the state were closed until Monday, education officials said.
Army and paramilitary personnel have been deployed to reach those trapped, but bad weather prevented rescue helicopters from lifting those stranded in many places.
Patel said that several areas had witnessed as much rainfall in the past few days as they would usually see throughout the three-month monsoon season.
He added that 39 of Gujarat's 187 large and medium-size dams are overflowing.
Most of India is currently in the grip of monsoon rains which sweep the country from June to September.
In many places, the monsoon rain volumes are below average, but in Gujarat the torrent has caused havoc.