A delay to Bangladesh's monsoon season is posing a severe risk of drought in the impoverished nation and threatening food supplies, officials warned Tuesday.

Monsoon rains normally sweep Bangladesh from June to September and the South Asian country gets more than 75 percent of its annual rainfall during this period but a lack of rain is hampering crop potential.

"For weeks there have been no rains in the northern and central districts, the country's main food belt. Tens of millions of farmers could not sow summer rice as their farmlands have dried up," said Ruhul Amin, the government's food planning chief.

"If no rain comes in the next couple of weeks, it will be a severe drought," he added.

The head of the government's weather department, Arjumand Habib, said rainfall during June was 37 percent below average while the first 19 days of July saw 23 percent lower precipitation than average for the period.

"What rains we've had since June were mainly concentrated in the northeastern and southeastern hilly areas, triggering flash floods there while causing drought-like situation in the plain lands," she said.

Scientists say Bangladesh is one of the countries worst affected by the effects of climate change with extreme weather conditions such as flooding and drought likely to increase in future.