The United Nations humanitarian agency is warning that about 5.7 million Pakistani flood survivors will face a serious food crisis in the next three months, as the death toll from the deluge rose on Monday.

Pakistan’s National Disaster Management Authority reported that floods fuelled by abnormally heavy monsoon rains have killed 1,695 people, affected 33 million more, damaged more than two million homes and displaced hundreds of thousands now living in tents or makeshift homes.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) said in its latest report that the current floods are expected to exacerbate food insecurity in Pakistan and added 5.7 million people in flood-affected areas will be facing a food crisis between September and November.

Even before the floods, according to the World Health Organisation, 16% of the population was living in moderate or severe food insecurity.

However, Pakistan’s government insists that there is no immediate worry about food supplies, as wheat stocks are enough to last through to the next harvest and that the government is importing more.

The UN agency said in a tweet on Monday that the agency and other partners have scaled up their flood response and delivered aid to 1.6 million people directly affected by the deluges.

The OCHA said outbreaks of waterborne and other diseases are on the rise in Sindh and south-western Baluchistan provinces, where floods have caused the most damage since mid-June.

Several countries and UN agencies have sent more than 131 flights carrying aid for survivors, but many are complaining they have either received too little help or are still waiting for it.

The UN humanitarian agency also said in its report that rainfall in Baluchistan and Sindh lightened substantially over the past week, as temperatures start to decrease ahead of winter.

The OCHA report also highlighted the ordeal of flood survivors, saying many continue to live in “unsanitary conditions in temporary shelters, often with limited access to basic services, compounding the risk of a major public health crisis”.

It said pregnant women are being treated in temporary camps when possible, and nearly 130,000 pregnant women need urgent health services.

“Already before the floods, Pakistan had one of the highest maternal mortality rates in Asia, with the situation likely to deteriorate,” it said.

The UN is due to issue a revised appeal seeking an additional 800 million dollars (£716 million) from the international community to respond to the soaring life-saving needs of Pakistani flood survivors.

Pakistan says floods caused damage worth about 30 billion dollars (£26.8 billion) to its economy.