Monsoon rains over the past week swelled three major rivers that cut through Punjab province, Pakistan's agricultural heartland and home to nearly half of its 255 million people.

"The incident happened when an underwater object hit Rescue 1122 boat," the provincial disaster management authority's director general Irfan Ali Kathia told local media.

"Ten other people were rescued but unfortunately five people lost their lives in the incident," he added of the incident late Saturday.

The flooded rivers have affected mostly rural areas near their banks but heavy rain also flooded urban areas, including several parts of Lahore -- the country's second-largest city.

While South Asia's seasonal monsoon brings rainfall that farmers depend on, climate change is making the phenomenon more erratic, and deadly, across the region.

Landslides and floods triggered by heavier-than-usual monsoon rains have killed more than 850 people nationwide since June.