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!" he added, also giving no details.

 

An explosion on a London Underground train on Friday was caused by an "improvised explosive device," British police said.