Pakistan has issued a flood alert for some southern districts, warning of torrential rains, as rescue teams continued searching for missing people in the northwest, where severe floods have killed hundreds over the past week.

At least 21 people have died in monsoon rain-related incidents in Pakistan, authorities said, pushing the nationwide death toll over the last week above 400 as floods and landslides continue to devastate large parts of the country.

A deluge of rain triggered floods and landslides, sweeping people away and flooding and destroying homes, officials said.