Two people have been arrested by police investigating the murder of a woman who was found strangled last week.

The naked body of Julie Hamill, 28, was discovered by a jogger on a beach in Portstewart, County Londonderry last Thursday.

Detectives now believe there was a sexual motive behind the killing. At an earlier stage of the investigation they said she had not been sexually assaulted.

Ms Hamill's heartbroken brother, Martin, made an appeal for information about the killing.

He said the murder of his sister had devastated the family.

"She was a beautiful girl, a caring, giving and generous person. Everybody said how bubbly she was and that was true."

"She was a super, great girl. The family are completely shattered. A big black hole has been left in our lives."

Police have carried out extensive inquiries to track down Ms Hamill's killer and establish her final movements.

The dead woman, who was a niece of the South Down Social Democratic and Labour Party MP Eddie McGrady, was strangled sometime after leaving a nightclub a mile along the coast in Portrush, where she lived.

Police now say she was helped out of Kelly's nightclub in Portrush by a man and a member of staff.

The employee then returned inside and a second man joined the other suspect who was holding the victim. It is these two men the police are keen to find.

The victim's clothing, including a denim jacket and black trousers, was found on a link road between Portrush and Coleraine, which is more than three miles from the nightclub. These are being forensically examined.

Police staged an information gathering operation in the north west exactly a week after the brutal killing.

On Wednesday night officers visited the Portrush nightclub where she was last seen alive and spoke to customers.

They set up a mobile police station and interviewed a large number of people about the killing.

Around 50 detectives and uniformed officers were involved in the seven hour operation which continued into the early hours of Thursday morning.

The officer leading the murder hunt has also confirmed that police are following a number of leads but are still keen for more people to come forward.

Detective Chief Inspector Hamilton Houston said a girl in a "helpless condition" who was seen being escorted from God's Lounge in Kelly's to a car, was Miss Hamill.

He added: "I would find it unbelievable that any member of the public could shield those responsible.

"We will leave no stone unturned until the perpetrator or perpetrators are caught but this can only be achieved through the assistance of the public. "

Police are still trying to establish a motive for the killing which has shocked people in the quiet seaside resort, frequented by holidaymakers.

Miss Hamill had been a part time guidance officer at the Causeway Institute of Further and Higher Education in Ballymoney, County Antrim but she lived in a flat in Portrush.