"The terrorists were arrested and some bombs and a huge amount of explosives were seized."
The arrests on Thursday resulted partly from evidence seized during police raids in December 2014, a police statement said.
"Terrorist organizations overseas have targeted your communities. They seek to pull your youth into the pit of violent extremism. Help us to help...
"We are treating this as a terrorist incident," Richard Walton, who leads the Counter Terrorism Command at London's Metropolitan Police...
A daily said the attacker was an 18-year old woman, but there was no confirmation.
The target was "rejectionists", as the group refers to Shi'ite Muslims.
The deadliest attack hit the northern Shaab neighborhood, where a car bomb followed by a suicide blast killed 19 people.
bombing of a Shi'ite Muslim mosque on Friday killed 27 people
Yassim Salhi was known to French authorities as a potential risk because he visited Islamists.