Pakistan called on the world Tuesday to speed up relief efforts after torrential rains exacerbated major floods, killing 270 people and making another 200,000 homeless in the south of the country.

Local officials say devastation in parts of the country's main breadbasket is worse than last year, when a fifth of the country was left under water by the country's worst ever floods that affected a total of 21 million people.

The government is trying to fend off criticism of an inadequate response to the floods for a second year running, by urging the international community to step up help to already aid-dependent Pakistan.

For months, aid groups had warned the government to invest in adequate prevention measures to mitigate against seasonal rains, avoid a repeat of last year's $10 billion losses, and protect those left vulnerable two years running.

"At least 270 people have died so far because of falling roofs, drowning in flooding waters and subsequent diseases among the affected families," said Sajjad Haider Shah, a disaster management official in southern Sindh province.

Government officials say at least 5.3 million people and 1.2 million homes have been affected, with 1.7 million acres of arable land inundated.

But a spokesman for Pakistani charity Pattan, working in the affected areas, feared that up to 10 million people could be at risk.

"Estimates show that 1.2 million houses are affected and people are really in a bad condition, so that's why I'm saying this figure must be close to double," Sarwar Bari, Pattan's national coordinator and spokesman, told AFP.

Pakistan's meteorological department says average rainfall across Sindh is three times normal, with the worst-affected districts of Badin, Mirpurkhas and Thar seeing eight times the usual levels.

Chief meteorologist Mohammad Riaz told AFP the figures were a 51-year record, and the rains would continue for the rest of the week.

The UN's World Food Programme agency is working to provide emergency supplies to half a million people.

The United States, whose relations with Pakistan nosedived after American troops killed Osama bin Laden near Islamabad in May, says it is sending food aid for nearly 350,000 Pakistanis and medical assistance for about 500,000.

Yousuf Talpur, an MP for the main ruling Pakistan People's Party, said his home district of Umerkot was almost entirely inundated and that little effort was being made to provide relief.

"My party is in government, yet I won't hesitate to say it is yet to go in full throttle to provide relief to our people," he said.

In the southeastern town of Sanghar, most of the 125,000 residents have left home because of flooding, said local official Anwer Narejo.