Typhoon Haiyan is battering the central Philippines with sustained winds of up to 199 mph. Meteorologists say that if initial estimates based on satellite images are borne out, it could be the most powerful storm ever to make landfall.The storm has forced millions to seek shelter in 20 provinces. At least three people have died, but it may take days before the full damage is known.
The region was already struggling after a powerful earthquake last month.
The authorities have warned that more than 12 million people are at risk from the storm — the equivalent of a category five hurricane.
It has so far lashed central islands, including Leyte and Samar, and the northern tip of Cebu, including Cebu city, the country's second largest with a population of 2.5 million.
Two people were electrocuted in storm-related incidents and another was killed after being struck by lightning, according to officials. Seven others were reported injured.
Reports say power and communications have been almost completely lost in Samar, Leyte and Bohol.
Save the Children Philippines Director Anna Lindenfors predicted a high casualty rate.
"We expect the level of destruction caused by Typhoon Haiyan to be extensive and devastating, and sadly we fear that many lives will be lost," she said in a statement.
[asset-pullquotes[{"quote": "We expect the level of destruction caused by Typhoon Haiyan to be extensive and devastating, and sadly we fear that many lives will be lost.", "style": "inset"}]]Former BBC Manila correspondent Kate McGeown says that while reports are now coming in from some of the affected cities, there is still very little information from the countryside in large areas of the Visayas region such as Negros and Iloilo, and the island of Mindoro.
The storm, known locally as Yolanda, was not expected to directly hit the capital Manila, more than 370 miles to the north.
Mai Zamora, from the charity World Vision, in Cebu, told the BBC: "The wind here is whistling. It's so strong and the heavy downpours are continuing."
"We've been hearing from my colleagues in [the city of] Tacloban that they've seen galvanized iron sheets flying just like kites."
Schools and offices closed, while ferry services and local flights were suspended. Hospitals and soldiers are on stand-by for rescue and relief operations.
The US Navy's Joint Typhoon Warning Centre said the typhoon was set to exit the Philippines after 9:00 p.m. local time.
Our BBC correspondent says that, while the country is better prepared than for previous storms, it is not clear whether even buildings being used as storm shelters can withstand these winds.
Waves as high as 45 ft could be seen around the coast, and there was 15.75 inches of rain in places.
In its path are areas already struggling to recover from a deadly 7.3 magnitude earthquake last month, including the worst hit island of Bohol where about 5,000 people are still living in tents.
Meteorologists in the Philippines warned that Haiyan could be as devastating as Typhoon Bopha in 2012, which devastated parts of the southern Philippines and left at least 1,000 people dead.
It is the 25th tropical storm to enter Philippine territory this year.