President Donald Trump reacted to a terrorist attack in London, pointing out that the world has to be tougher on terrorism.

“Another attack in London by a loser terrorist,” Trump wrote. “These are sick and demented people who were in the sights of Scotland Yard. Must be proactive!”

An explosive device exploded on a London commuter train on Friday, injuring 22 people. The incident is being investigated as an act of terror.

In response, the president called for a “larger, tougher” travel ban in the United States:

He also asserted that he had made more progress in the war against the Islamic State (ISIS) than former President Barack Obama.

“Must be proactive & nasty!” he wrote: