Trump tweeted: "At least 7 dead and 48 wounded in terror attack and Mayor of London says there is 'no reason to be alarmed!'"
Revellers shouted and threw barstools at the three attackers, who killed seven and injured 49.
One person was hit with a stray bullet and is being treated at hospital along with more than 40 other people injured in a knife and van attack in London Bridge and Borough Market.
Like the Bataclan and Manchester Arena, Borough Market was targeted for being a place of celebration and joy.
Tourists and locals spent the night in hotels after the attack that killed seven people and injured dozens.
On social media, people reported being told to go into bars and restaurants and and take cover under tables.