More than one thousand people have been killed by heavy monsoon rains that lashed through Pakistan's north-west region last week.

According to official sources, over 1,500 people have been killed and 1.5 million affected in some of the worst flooding to hit Pakistan in recent years.

Christian aid groups in the country are assisting in relief efforts by distributing food packages and shelter material such as plastic sheeting.

The scale and magnitude of this year's floods are far greater than in recent monsoon seasons, with tragic and deadly results, said global humanitarian organisation Church World Service.

Apart from food and shelter, CWS has mobilised a mobile health unit to provide emergency medical assistance for flood-affected families.

Given the problems facing disaster responders, it is even more important "to apply strict measures of transparency and quality management", said CWS-P/A Deputy Director Shama Mall. "We need to be good stewards of limited available resources while helping as many as possible."

Christian development agency World Vision is also planning a rapid response to the floods.

The group warned that children and women already suffering as a result of poor health and unhygienic conditions are most at risk.

"There is now a real danger of the spread of water-borne diseases and possibly cholera, as well as complications such as respiratory problems and skin allergies," said Shaharyar Bangash, World Vision's program manager, from Peshawar.

"Drinking water is the most urgent need now, even more than food. Children have been wearing the same muddy clothes for three days now, and many of them have visible skin diseases," he added.

Meanwhile, the aid group's director in Pakistan warned that funds were running low.

"The needs are massive right now, and World Vision has the experts and plans to help thousands. But without funding from international donors, our response will be severely limited," said World Vision's Edward Aquino from Islamabad.

UN Secretary-General Ban Ki-moon on Sunday said he was "deeply saddened by the significant loss of lives, livelihoods, and infrastructure" in Pakistan.

A UN statement said: "The secretary-general offers his deepest condolences to the people and government of Pakistan and reiterates the UN's full commitment to supporting the national and provincial authorities in meeting the humanitarian needs of the population affected."