* Cyclone Phailin kills at least five so far
* Storm could affect 12 million
* Operations at port halted; major gas field spared
A fierce cyclone tore into India's coast, killing at least five people, forcing half a million into shelters and threatening to devastate farmland and fishing hamlets.
Cyclone Phailin was expected to remain a "very severe cyclonic storm", packing winds of up to 210 kph (130 mph), into Sunday before steadily weakening as it moves inland in the states of Odisha and Andhra Pradesh.
The storm snapped trees and electricity poles and smashed windows in Brahmapur, a town in the area where it hit land on Saturday evening.
Rescue workers and soldiers spread out across the region in helicopters and trucks and the full extent of destruction was only expected to become clear after daybreak on Sunday.
Some 12 million people were in the path of Phailin, weather and disaster management officials said. It was India's strongest cyclone since a typhoon killed 10,000 people in the same region 14 years ago. Aid agencies hope better preparation and early warnings will mean far fewer casualties this time.
Satellite images showed a vast spiral-shaped storm covering most of the Bay of Bengal's warm seas, before it churned inland.
Jagdesh Dasari, a leader in the fishing village of Mogadhalupadu, said police ordered villagers to leave their mud and thatch huts for a school building as night fell. Many on the impoverished coast were reluctant to go, afraid of losing belongings.
"Many people refused to move, had to be convinced, and at times the police had to forcefully move them to safe places," Home Minister Sushilkumar Shinde said.
In the first reported deaths, four people were killed by falling trees, while another died when the walls of her mud house collapsed. Electricity went out in several towns, including Odisha's capital Bhubaneswar.
"We are fortunate that we are here ... we saved our lives," said Narayan Haldar, huddled with 1,300 people in an Odisha fishing village storm shelter, built after the 1999 typhoon.
But he complained the government had not provided food. Some shelters were dilapidated and TV images showed crowds standing in the rain outside one overcrowded building.
Large waves pounded beaches and villagers told a television station that surging sea levels has pushed water hundreds of feet (metres) inland in low-lying areas.
Higher sea levels driven by storm surges can cause the worst destruction. Phailin was forecast to drive sea levels up 11 feet (3.5 meters) at its peak.
"The biggest threat right now is the storm surge along the coast," said Eric Holthaus, meteorologist for Quartz magazine.
India's disaster preparations have improved since the 1999 storm and aid workers praised the precautions taken, such as the stocking of rations and evacuations.
Some 550,000 people were crammed into makeshift shelters including schools and temples, in what the National Disaster Management Authority called one of India's largest evacuations.
Even before landfall, coconut trees in villages along the coast were bent and broken in the gusting wind. Electrical poles were brought down and roads littered with debris.
Terrified children clung to their mothers as they sought shelter. Most towns along the coast were deserted but some people were still trying to flee in buses and three-wheeled auto-rickshaws just hours before the storm struck.
The size of the storm made extensive damage to property more likely, Shashidhar Reddy, vice chairman of the National Disaster Management Authority told reporters in New Delhi. "Our priority is to minimise loss of life," he said.
The weather department warned mud houses faced destruction. It said the disruption of power and communication lines and the flooding of railways and roads was likely.
London-based Tropical Storm Risk said the storm lost some strength before making landfall as Category 4 - the second strongest such rating. The U.S. Navy's weather service said wind at sea was earlier gusting at 296 kph (184 mph).
"A lot has been learnt since 1999 and my guess is that while there could be extensive damage to property and crops, the death toll will be much less," said G. Padmanabhan, emergency analyst at the U.N. Development Programme.
Despite the warnings, some refused to leave their homes.
"I have a small child, so I thought, how will I leave?" asked Achamma, 25, holding her son in Donkuru, a fishing village in Andhra Pradesh, as waves crashed on the beach.
The port of Paradip halted operations on Friday. All vessels were ordered to leave the port, which handles coal, crude oil and iron ore. An oil tanker carrying 2 million barrels of oil, worth $220 million, was moved, an oil company source said.
The storm landed far north of India's largest gas field, the D6 natural gas block in the Cauvery Basin further down the east coast, operated by Reliance Industries.