India's western states of Gujarat, Maharashtra, Goa and other coastal regions are on alert after meteorologists warned that a cyclonic storm over the Arabian sea would intensify over the next 24 hours.

Authorities have told fishing communities to halt operations for the next five days in the eastern and central Arabian sea, and along the Indian Saurastra and Kutch region, ahead of Cyclone Biparjoy.

The Indian Meteorological Department (IMD), which categorised Biparjoy as a "very severe storm", said at 08:30 a.m. IST (0300 GMT) on Saturday the weather system was centered about 620 kilometres (385.25 miles) west-southwest off the financial capital Mumbai.

"It is very likely to intensify further and move north-northeast wards gradually during next 24 hours," the IMD said in a statement on Saturday.

It warned of heavy rainfall at isolated places in the state of Kerala and coastal Karnataka region in next three days.

The IMD had expected monsoon rains to arrive over the southernmost state of Kerala on June 4, but the formation of Biparjoy has delayed that.

In Gujarat, the 13 coastal districts of South Gujarat, Saurashtra peninsula and Kutch have been put on alert.

"We are fully prepared to deal with any situation," Kamal Dayani, additional chief secretary in the state revenue department, told Reuters.

Teams from the National Disaster Response Force and State Disaster Response Force have been deployed in the districts likely to be affected by the storm.

Unstable structures, such as hoardings, have been removed and the electricity department is on standby for power supply disruptions.