"As Londoners, we will stand together in solidarity to remember those who were killed or injured in this horrific terror attack," Khan said in a statement. “There can be no justification or excuses for these barbaric, cowardly attacks."
He continued, “By standing together as a city we will send a powerful message here and around the world — that Londoners will never be cowed by terrorism."
The attackers targeted innocent bystanders on Saturday evening — plowing a van into pedestrians on London Bridge before emerging from the vehicle and stabbing bystanders at the nearby Borough Market, a lively area filled with bars and restaurants. Three suspects were fatally shot by police.
The vigil is being held near London's City Hall at Potters Fields Park, which is on the bank of the river Thames. Watch it live above at 1 p.m. E.T..