Netherlands police arrest ex British student over mass shooting threat in Leiden.

Dutch police have arrested a suspect after a threat to kill a teacher and students sparked a shutdown of schools in the city of Leiden.

Authorities ordered 22 schools to remain closed after a warning was posted online over the weekend.

The anonymous threat was posted on US based website 4chan.org.

"I will shoot my Dutch teacher and as many students as I can," the message in English read.

"It's at a school in the Dutch city of Leiden and, for more proof, I will be using a 9mm Colt Defender.