The 34-year-old suspect was arrested on Thursday morning and is one of three arrested to date – the first two have been released in bail pending further police enquiries.
Police have sought the additional time as they continue to probe the “brutal” execution-style murder of Mr Lovell, which happened in the Ardcarn Park area of the city shortly before 6pm on Thursday, December 1.
It comes a day after detectives revisited the scene of the “ruthless murder”.
Detective Chief Inspector John Caldwell, speaking last night, said: “We want to jog memories, and are keen to encourage anyone with information, no matter how insignificant it may seem, to speak up.
“This was a planned and shocking attack, which blatantly took place at a time – just after 6pm – when people would have out and about.
“Our appeal is backed by an award of up to £20,000 from Crimestoppers, and I’m keen to stress that information can be given anonymously. Crimestoppers will never ask for or store any of your personal details.”
The charity, who are independent of the police, is offering the reward for information it receives that leads to the arrest and conviction of those responsible for Mark’s murder. Contact Crimestoppers on freephone 0800 555 111 or online at www.crimestoppers-uk.org