Roaring winds and heavy rains were already lashing both states as the cyclone moved from the Bay of Bengal towards the coast. hit their coast by Saturday evening.
The Indian Meteorological Department (IMD) said the "very severe" Phailin now lay about 310 km south-southeast of Paradip in Odisha and it could hit the land between 6 and 8 p.m. with wind speeds of 210-220 kmph.
IMD officials said it was likely to retain its intensity six hours after the landfall.
Parts of Odisha and Andhra coasts have received eight to 10 cm rainfall accompanied by high winds since Friday night. The IMD has forecast heavy to very heavy rains in coastal Odisha, north coastal Andhra and isolated heavy rains in West Bengal.
The storms would inundate low lying areas of Ganjam, Khurda, Puri and Jagatsinghpur districts of Odisha and Srikakulam in Andhra Pradesh, said officials.
About three lakh people in Odisha and 64,000 in north coastal Andhra were evacuated to safer places. The army, navy and air force and the National Disaster Response Force (NDRF) were on alert for rescue and relief work.
The evacuation of people from low-lying area along the Odisha coast continued Saturday.
Special relief commissioner Pradeep Kumar Mohapatra told IANS that the wind speed was picking up in several areas. In Ganjam, it had reached 60-80 kmph and the sea was witnessing high tide.
The cyclone, expected to make landfall in Gopalpur in Ganjam district, is likely to damage crops and property in the coastal districts of Ganjam, Gajapati, Khordha, Puri and Jagatsinghpur. Many other districts were also likely to be affected.
Heavy to very heavy rainfall is expected at most places. Some places may witness extremely heavy falls of about 25 centimeters, the weather office said.
Eighteen fishermen, who went for fishing in the Bay of Bengal in a trawler over a week ago, were stranded in the sea in Astaranga area of Puri. The Coast Guard has been told to rescue them, police told IANS.
Many low laying areas in Odisha were inundated due to heavy rains. Road communication have been disrupted in some places of Ganjam and Jagatsinghpur districts. Power lines have also hit.
The government said food grain and other essential commodities have been stocked in cyclone relief centres. People taking shelter in these centres were provided cooked food.
At least 28 teams of NDRF would be pressed into relief and rescue work, and 20 of them have reached the vulnerable area.
About 10 choppers have been kept in West Bengal for air dropping relief materials as the Bhubaneswar airport may be affected by the rough weather.
Over 64,000 people were evacuated from low lying areas near the coast in Srikakulam, Vizianagaram and Visakhapatnam districts in Andhra Pradesh. Authorities went on high alert in all nine coastal districts.
Andhra Pradesh Minister for Relief and Rehabilitation N. Raghuveera Reddy said in Visakhapatnam that the army, navy and NDRF were on standby and helicopters were ready for rescue work.
In Srikakulam district, heavy rains since Friday night inundated several low-lying villages. Fishermen have been told not to venture into the sea.
The railways have cancelled all trains in north coastal Andhra including services between Andhra and Odisha. Air services between Visakhapatnam and Bhubaneswar have also been suspended.