Fishermen shift their boats to safer grounds as a precaution against Cyclone Yaas in Odisha, India. AP
The cyclones are hitting as India reels from a surge in coronavirus infections that has plunged the healthcare system into crisis and pushed the country's Covid-19 death toll above 300,000.
Experts say storms off India's coast are increasing in frequency and intensity as climate change warms ocean waters.
The India Meteorological Department said Cyclone Yaas had formed in the Bay of Bengal and was expected to barrel into West Bengal and Odisha states on Wednesday.
Neighbouring Bangladesh has also been put on alert.
Yaas could pack gusts of up to 185 kilometres (115 miles) per hour as a "Very Severe Cyclonic Storm" at the time of landfall, the department said.
This satellite image shows a cyclone (right) approaching eastern India on Sunday. RAMMB/CIRA/AFP
Storm surges of up to four metres (13 feet) high were "likely to inundate low-lying coastal areas", it added.
evacuations in coastal districts and the Sunderbans mangrove forest, a UNESCO world heritage site, started on Sunday, West Bengal disaster management minister Javed Ahmed Khan said.
"We have to evacuate nearly half a million people... to schools (and) government offices, which have been turned into cyclone centres to provide shelter to these people," Khan told AFP.
The military and disaster teams have been deployed to help with the preparations and potential rescue operations, Prime Minister Narendra Modi said on Sunday.
Last Monday, Cyclone Tauktae — India's first major tropical storm this season — slammed into the western state of Gujarat.
It battered several states with torrential downpours and strong winds.
The death toll from Tauktae rose to at least 155 on Monday after more bodies were recovered from an oil rig off the western city of Mumbai and several support vessels, the navy said.
In Sri Lanka, the weather bureau warned the island nation's fishermen not to venture into the Bay of Bengal.Agence France-Presse
Cyclones are a regular menace in the northern Indian Ocean but many scientists say they are becoming more frequent and severe as climate change warms sea temperatures.
The Indian Meteorological Department said landfall began around 9am (0330 GMT) and warned that it would generate waves higher than rooftops in some areas. Coastal areas experienced wind gusts up to 155 kilometres an hour and pounding rain.
Scientists say cyclones in the densely-populated region, currently reeling from coronavirus, are becoming both more frequent and stronger as climate change leads to warmer sea temperatures.
The death toll from floods and landslides in India rose to 85 on Wednesday, officials said, while Nepal also reported 43 fatalities and 43 missing.
Infections have been reported in more than 210 countries and territories since the first cases were identified in December 2019.
There have been several attacks this year on army vehicles in eastern Syria by suspected Daesh militants who still operate in the sprawling desert area