Facebook has activated its Safety Check feature after torrential rains lashed Karachi on Thursday.

Users of the social network can use the Safety Check Tool to reassure contacts they are "safe" and check up on friends who are in the area.

At least 21 people died after the metropolis was battered with heavy rainfall on Thursday which saw Army contingents being deployed to assist in rescue efforts.

To mark yourself as safe you can visit ?The Flooding in Karachi, Pakistan? page.

The page has been flooded with people offering their services as volunteers to help those in need of shelter and food.

People are also using the page to request for food, water, and other items needed by those displaced by the heavy downpour in the metropolis.