The man suspected of driving a van into Muslim worshippers near a north London mosque is Darren Osborne from Cardiff, the BBC understands.
One man died at the scene and 10 people were injured after the van mounted a pavement near Finsbury Park Mosque.
An address in Cardiff is being searched while the van belonged to Rhondda Cynon Taff hire firm Pontyclun Van Hire.
Police said a 47-year-old man was held on suspicion of attempted murder and alleged terror offences.
Mohammed Alamgir Ahmed from Muslim Council of Wales, said Muslims were easy targets as Ramadan comes to an end.