President Donald Trump on Friday blasted the “loser terrorists” behind the train attack in London that injured at least 18 people.

“Another attack in London by a loser terrorist,” the US president tweeted. “These are sick and demented people who were in the sights of Scotland Yard. Must be proactive!”  He then added: “Loser terrorists must be dealt with in a much tougher manner,” without giving details of what that meant.

“The internet is their main recruitment tool which we must cut off & use better!” said the US president, also giving no details. An explosion on a London Underground train on Friday was caused by an “improvised explosive device,” British police said.