By Amanda Ferguson
Belfast (Reuters) - Northern Irish police arrested a fifth man on Friday in relation to the attempted murder of a senior detective shot in front of his young son in the town of Omagh.
A 43-year-old man was arrested in the Stewartstown area of County Tyrone under anti-terrorism laws and is being questioned by detectives, the Police Service of Northern Ireland said in an statement.
Four men aged 22, 38, 45 and 47 arrested earlier in connection with the attack remain in police custody.
Detective Chief Inspector John Caldwell is in critical condition after undergoing surgery. He was shot a number of times by two gunmen on Wednesday evening while putting footballs in his car after finishing a coaching session with an under-15 soccer team.
While a 1998 peace deal largely ended three decades of sectarian violence in Northern Ireland, police officers are still sporadically targeted by splinter groups of mostly Irish nationalist militants opposed to Britain's rule over the region.
Assistant Chief Constable for Crime Department Mark McEwan on Friday confirmed that Northern Irish police are treating the attack on Detective Chief Inspector Caldwell as "terrorist-related" and its primary line of enquiry is Irish nationalist militant group the New IRA.
(Reporting by Amanda Ferguson; Writing by Graham Fahy; Editing by Sandra Maler)