At least 13 people were killed and many remained missing after a boat carrying around 25 flood victims capsized in the swollen Indus River in Pakistan's Sindh province on Monday, local media reported.

The incident took place in Bilawalpur village in Sindh's Sehwan city when a boat taking flood victims from submerged villages to a safer location capsized. The deputy commissioner said that the death toll rose to 13; while eight people have been rescued.

Rescue sources said that nearly 25 flood victims were being taken to the relief camps when the incident took place, Geo News reported. This comes as the Pakistan government and the military are underataking relief operations in flood-affected areas.

The humanitarian situation in Pakistan has deteriorated over the past two weeks as heavy rains continue to cause flooding, and landslides resulting in displacement and damage across the country, according to the UN Office for the Coordination of Humanitarian Affairs (OCHA).

The National Disaster Management Authority (NDMA) reported some 33 million people in Pakistan have been affected. Over 218,000 houses have been destroyed and a further 452,000 damaged since June 14, according to the NDMA.