The South Asian nation of 170 million people, crisscrossed by hundreds of rivers, has seen frequent floods in recent decades.

It is among the countries most vulnerable to disasters and climate change, according to the Global Climate Risk Index.

A bulletin from the disaster ministry today said: “4.5 million people have been affected, and 13 people have died across the country”.

Nearly 190,000 others were taken to emergency relief shelters, according to the bulletin.

Altogether, 11 of the country’s 64 districts were affected by the flooding, the bulletin added.

Feni, about 100km northwest of the main port city of Chittagong, was worst-hit.

“It’s a catastrophic situation here,” rescue volunteer Zahed Hossain Bhuiya, 35, told AFP in Feni.

“We are trying to rescue as many people as we can.”