Vietnam is suffering its worst drought in nearly a century with salinisation hitting farmers especially hard in the crucial southern Mekong delta, experts said Monday.

"The water level of the Mekong River has gone down to its lowest level since 1926, leading to the worst drought and salinisation there," Nguyen Van Tinh, deputy head of the hydraulics department under the Ministry of Agriculture, told AFP.

The low-lying and heavily cultivated Mekong region is home to more than 20 million people and is the country's rice basket.

Intensive cultivation and rising sea levels already make it one of the world's most ecologically sensitive regions.

Scientists blame the ongoing 2015-2016 El Nino weather phenomenon, one of the most powerful on record, for the current drought.

Water shortages have also hampered agriculture in nearby Cambodia, Laos, Thailand and Myanmar.

Le Anh Tuan, a professor of climate change at the University of Can Tho in the heart of the Mekong region, said as much as 40-50 percent of the 2.2 million hectares (5.4 million acres) of arable land in the delta had been hit by salinisation.

"We do not have any specific measures to mitigate the situation," Tuan told AFP, adding that residents had been urged to save water for domestic rather than agricultural use.

Vietnam's communist rulers have announced $3.8 million of financial assistance for affected areas.

The nation is the world's second largest exporter of rice and coffee, two crops that are particularly vulnerable to drought.

Severe cold and drought hit Vietnam's lucrative coffee industry in 2013 and 2014.

Vietnam's rice yields have nearly quadrupled since the 1970s, official figures show, thanks to high-yield strains and the construction of a network of dykes that today allow farmers to grow up to three crops per year.