In the UK, 10 people have been injured after a van was driven into a group of worshippers in a terrorist attack outside a mosque in north London.
One man has died, although police say he'd already been receiving first aid.
An Imam shielded the suspected driver from an angry crowd until police arrested him.
Police have deployed extra resources to reassure communities - but say the attacker "acted alone".
The British Prime Minister Theresa May's chaired a meeting of the government's Cobra emergency committee: