MANILA - The Philippines warned Wednesday there was a high probability of epidemics among the 340,000 people crowded into poorly equipped makeshift evacuation centres following recent deadly floods.

As the government also admitted it had no idea when those left homeless in the September 26 disaster would be resettled, international aid agencies stepped up their efforts to help the flood victims.

"Epidemic potential in some areas is very, very high," Health Secretary Francisco Duque told reporters after visiting one camp housing 8,000 people in a northern part of Manila, the nation's capital.

The government has already faced fierce criticism for its response to the disaster, which claimed at least 295 lives when tropical storm Ketsana dumped the heaviest rains in over four decades on Manila and neighbouring areas.

Duque said that, 11 days after the floods, only 240 portable toilets had been delivered to the more than 500 evacuation shelters that had been set up at gymnasiums, schools and large sports arenas.

In the camp at suburban Marilao that he visited, Duque said an average of about 100 people daily had been complaining of diarrhoea and the number was increasing.

"Marilao is just an example. Certainly what's happening there could be a reflection of what may be happening in other affected areas," he said.

In the first few days after the floods, the government said it feared disease outbreaks such as swine flu, diarrhoea and the bacterial disease leptospirosis.

But Duque's comments were the strongest from the government about a potential health crisis involving flood survivors.

The burden for overstretched relief workers increased when Typhoon Parma slammed into the northern Philippines exactly a week after Ketsana, killing at least 16 and flooding large swathes of farmland.

Many areas in Manila and the northern provinces remain flooded, forcing many thousands of people to live in flooded villages or cities with their homes still partly submerged.

Defence Secretary Gilberto Teodoro said government efforts were focused on relief operations, and that resettling those living in the evacuation centres remained a long way off.

"It's not possible to give a time frame," he said when asked about resettlement.

Teodoro said government was tapping engineers to come up with a new urban plan, but just repairing destroyed bridges, dykes and roads would be the main priority in the next six months.

Meanwhile, the United Nation's resident coordinator to the Philippines, Jacqueline Badcock, said a flash appeal for 74 million dollars issued by the world body in Geneva on Tuesday would go to about one million people.

"With flood waters yet to recede from many affected areas, access to populations in need of assistance continues to be challenging," she said.

"It is predicted that some areas will remain under flood waters for up to two months."

The UN's World Food Programme country director Stephen Anderson said earlier that agency had used boats and helicopters to deliver food, while the US military had also mobilised air assets to help in the effort.

US President Barack Obama on Tuesday sent condolences to the Philippines, and said his government had set aside 1.8 million dollars for its Southeast Asian ally to help deal with the floods.