TEHRAN: Two million people are in desperate need of humanitarian aid after the devastating floods that have swamped many parts of Iran since March, the Red Crescent said on Monday.

The International Federation of Red Cross and Red Crescent Societies called the floods the "largest disaster to hit Iran in more than 15 years."

According to the IFRC, the floods have killed at least 78 people and injured more than 1,000 others.

Estimates put the number of people affected at 10 million across 2,000 cities and towns, with more than half a million displaced, it said.

"In all, more than 457,000 people have been reached by Red Crescent services," and emergency accommodation provided for 239,000 more.

Heavy rainfall in eastern Iran since Saturday prompted authorities to renew flood warnings for large swathes of the country, with local media reporting rivers bursting their banks and roads being swept away.

Iran's Supreme Leader Ayatollah Ali Khamenei gave the government permission to use money from the National Development Fund should the country’s regular budget not meet the need.

Iranian president Hassan Rouhani asked Khamenei to release $2 billion from the fund, which was established in 2000 and is used in emergency cases.

Flash floods have been hitting the northern and western parts of Iran, with damages estimated so far at more than $2.5 billion.

Officials said Sunday that 25 out of Iran's 31 provinces have been affected and more than 14,000 kilometres (8,700 miles) of roads damaged.