The attack comes nearly two weeks after the Manchester bombing, which killed 22 people and injured 116.
Stars are sending their love to London after reports of several attacks around the city.
Nearly two weeks after England's Manchester bombing -- and one day before Ariana Grande's One Love Manchester benefit concert -- London's Metropolitan Police confirmed that the city was hit by two terrorist attacks, as a vehicle ran down pedestrians on London Bridge and individuals were stabbed at nearby Borough Market on Saturday.
Grande, who will headline her star-studded benefit concert at Old Trafford Cricket Ground on Sunday, quickly took to Twitter to share her prayers for London. The bombing at her Manchester Arena concert on May 22 killed 22 people and left 116 injured.
RELATED: How to Watch Ariana Grande's Star-Studded Manchester Benefit Concert
Demi Lovato also shared her well wishes, as other stars took to social media to react to the news.
Grande touched down in London on Friday to visit with fans injured in the Manchester attack ahead of Sunday's One Love Manchester concert. Katy Perry, Justin Bieber, Miley Cyrus and more will take the stage with Grande during the event, which will benefit the Red Cross' Manchester Emergency Fund.
See more on the event in the video below.