MANILA - The Philippines declared a nationwide state of calamity on Friday as a super typhoon bore down a week after flash floods killed nearly 300 people in and around Manila.

Typhoon Parma, about 150 km (100 miles) east of Luzon, was gaining strength as it churned west-northwest toward the mainland, bringing heavy rain.

It was expected to make landfall in or near the northeastern province of Isabela on Saturday. The area is mountainous and not heavily populated, but Parma was likely to lash Luzon with rain over the next two days, making life worse in flood-hit regions.

We're concerned about the effects of more rain on the relief work in flooded areas because the water level could rise again, Defence Secretary Gilberto Teodoro said in a briefing aired live on national television.

The Asia-Pacific region has been hit by a series of natural disasters in recent days, including Typhoon Ketsana which killed more than 400 in the Philippines, Cambodia, Laos, Thailand and Vietnam.

Tens of thousands were also displaced in southern Laos and flash floods were reported in northern Thailand.

Two powerful earthquakes rocked the Indonesian island of Sumatra, with the death toll likely to be in the thousands, and a tsunami battered American and Western Samoa, killing nearly 150.

In Taiwan, authorities identified 12 villages for mandatory evacuation ahead of Parma and another storm in the Pacific, Typhoon Melor.

The Taiwan government came in for heavy criticism after a deadly typhoon in August killed as many as 770 people.

In the Philippines, harsh criticism of the slow response to last week's floods could affect the chances of Teodoro in next May's presidential election, where he seeks to replace President Gloria Macapagal Arroyo.

Teodoro, also the head of the National Disaster Coordinating Council, has placed the military and police on alert and ordered civilian agencies to stockpile food, water, medicine, fuel and other relief supplies.

Arroyo declared a state of calamity across the country, which will allow local governments access to emergency funds for relief work.

She also ordered provincial governments to evacuate people living in low-lying areas in the path of Parma, by force if necessary.

Airlines also canceled about 26 domestic flights to four destinations in typhoon-affected areas in the central Philippines from 1 p.m. (0500 GMT) on Friday, airport authorities said.

The weather bureau said Parma, with gusts of up to 230 kph (143 mph) at the center, will be the strongest typhoon to hit the country since 2006.

It's still very much possible that we will raise signal number 4 as it closes in on northern Luzon, Prisco Nilo, head of the weather bureau, told reporters.

At signal number 4, residential and commercial buildings may be severely damaged, large trees uprooted, and power and communication lines may be cut.

Last week's storm, Ketsana, left hundreds of thousands homeless in and around Manila and areas around a lake near the capital remain submerged under 2-3 meter floodwaters. It also damaged or destroyed more than $108 million in crops, infrastructure and property.

The Philippines is hit by frequent typhoons in the summer which often continue on their track to hit Vietnam, China and Taiwan before weakening over land.

(Additional reporting by Ho Binh Minh in Hanoi, Ralph Jennings in Taipei, Martin Petty in Bangkok and Manny Mogato)

(Editing by Raju Gopalakrishnan and Jerry Norton)