Haiyan, a category-5 storm, lashed the islands of Leyte and Samar with 5-6 metre (15-19 ft) waves as it headed toward densely populated central and southern Philippines, including the resort island of Boracay and other holiday destinations. (Agencies)
Authorities warned more than 12 million people were at risk, including residents of the Philippines' second-largest city Cebu, home to around 2.5 million people, and areas still reeling from a deadly 2011 storm and a 7.1-magnitude quake last month.
"The super typhoon likely made landfall with winds near 195 mph (313 kph). This makes Haiyan the strongest tropical cyclone (typhoon) on record to make landfall," said Jeff Masters, a hurricane expert and director of meteorology at U.S.-based Weather Underground.
Typhoons and cyclones of that magnitude can blow apart storm-proof shelters due to the huge pressure they create, which can suck walls out and blow roofs off buildings, say engineers.
About a million people had taken shelter in more than 20 provinces, after Philippine President Benigno Aquino appealed to people in Haiyan's path to evacuate from danger spots, such as river banks, coastal villages and mountain slopes.
"Please do not underestimate this typhoon. It is very powerful. We can feel each gust," Roger Mercado, governor of Southern Leyte province, adjacent to Leyte, told DZBB radio. "We lost power and all roads are impassable because of fallen trees. We just have to pray."
"Our school is now packed with evacuees," an elementary school teacher in Southern Leyte who only gave her name as Feliza told a radio station. Leyte and Southern Leyte are about 630 km (390 miles) southeast of the capital Manila.
Authorities halted ferry services and fishing operations, while nearly 200 local flights had been suspended. Commuter bus services were also stopped as the storm dumped torrential rain and ripped iron roofs off buildings and houses.
Schools, offices and shops in the central Philippines were closed, with hospitals, soldiers and emergency workers on standby for rescue operations.
"We can hear the winds howling but the rains are not too strong. We have encountered several distress calls regarding fallen trees and power lines cut. We don't have power now," Samar Vice Governor Stephen James Tan said in a radio interview.
More than 41,000 people have been evacuated in his province, one of the country's poorest, said Tan.
The state weather bureau said Haiyan is expected to exit the Philippines on Saturday and move towards the South China Sea, where it could become even stronger and threaten Vietnam or China.
The world's strongest recorded typhoon, cyclone or hurricane to previously make landfall was Hurricane Camille in 1969, which hit Mississippi with 190 mph winds, said Weather Underground's Masters.
An average of 20 typhoons slam into the Philippines every year. In 2011, typhoon Washi killed 1,200 people, displaced 300,000 and destroyed more than 10,000 homes. Haiyan is the 24th such storm to batter the Philippines this year.
Typhoon Bopha last year flattened three coastal towns on the southern island of Mindanao, killing 1,100 people and causing damage estimated at USD 1.04 billion.
In September, category-5 typhoon Usagi, with winds gusting of up to 240 kph (149 mph), battered the northern island of Batanes before causing damage in southern China.
Haiyan, a category-5 storm, lashed the islands of Leyte and Samar with 5-6 metre (15-19 ft) waves as it headed toward densely populated central and southern Philippines, including the resort island of Boracay and other holiday destinations.