British police have arrested seven people suspected of terrorism offenses. Five were arrested in Wales Thursday, Dec 4, and two were arrested in London, the Associated Press reports.

The arrests follow a recent uptick in terror arrests as British police cope with an increasing number of Britons trying to join extremist Islamic State fighters in Syria.

There are concerns that some who have returned are plotting attacks in Britain.

Welsh police said the five were arrested because of suspected support for banned organizations.

A 33-year-old man was arrested in London on suspicion of involvement in terrorism and a 40-year-old man was arrested on suspicion of conspiracy to pass fraudulent documents.

Police say the two London arrests are linked to the earlier arrests of five other terror suspects.