British police are investigating an explosion in a West London subway station that injured at least 22 people during rush hour on Friday morning. The incident, which authorities are treating as terrorism, caused a fire on the train and sent a crowd of panicked commuters fleeing the scene.

Major attacks have hit European nations such as France, Belgium and Germany in recent years, but the United Kingdom had until this year mostly avoided large-scale terror events since the series of suicide bombings in London that killed 52 people on July 7, 2005.

However, Britain has reported foiling more than a dozen plots since 2013. And as authorities respond to a new series of attacks in 2017, terror-related arrests have risen to a record level in the U.K.

Here is a timeline of some of the major extremist attacks to hit Britain in the last 12 years:

2017 Finsbury Park Mosque Attack

A man driving a van struck pedestrians leaving Finsbury Park Mosque in North London on June 19, injuring at least 10 people. The assailants motive remains under investigation, but it is believed that he was self-radicalized into an extremist hatred of Muslims .

2017 London Bridge And Borough Market Attacks

Three men plowed a van into pedestrians on the London Bridge on June 3 before exiting the vehicle and stabbing other people at a restaurant in Borough Market, less than half a mile away.

Eight people were killed and nearly 50 were injured. The self-described Islamic State claimed responsibility.

2017 Explosion After Ariana Grandes Manchester Concert

A suicide bomber detonated an improvised explosive device near the Manchester Arena on May 22, moments after pop singer Ariana Grande wrapped up a concert at the venue. At least 22 people, including children, were killed, and 59 were injured in the explosion. Most victims were leaving the concert hall when the attack took place.

Manchester police identified the attacker as 22-year-old Salman Abedi, a British national whose parents came to the U.S. from Libya. Abedi was killed when the bomb was detonated. ISIS claimed responsibility for the attack in a statement released the following day.

The incident, which targeted young concertgoers and their families, was the deadliest on British soil since 2005 London bombings .