A 21-year-old man is being questioned over the murder of another man in Belfast on Thursday.
The 30-year-old died in hospital following an incident in the Parkmount Street area in the north of the city on Thursday night.
The Police Service of Northern Ireland (PSNI) has launched a murder investigation.
Detectives are appealing for witnesses to contact them on 101.
North Belfast MP Nigel Dodds has urged full co-operation with police.
"This has caused great shock in this settled and close-knit community off North Queen Street," the DUP representative said.
"I wish to appeal for full co-operation with the police, in what is now a murder investigation.
"Our thoughts and prayers are with his man's family and friends at this time of sudden bereavement."
SDLP North Belfast MLA Nichola Mallon also expressed shock.
"I was shocked and saddened to hear that a 30-year-old man was murdered in North Belfast last night," she said.
"My thoughts and the thoughts of my colleagues are with the man's family and friends at this incredibly difficult time.
"I would appeal to anyone who has any information to contact the police or Crimestoppers."
On Friday morning people on Parkmount Street expressed their shock.
One pensioner, who lives on the section of the street where the incident happened, said she did not hear anything until an ambulance arrived.
"It was just after 9pm, I had gone up to bed to read a book because I didn't like the film he (her husband) was watching," said the woman, who did not want to be named.
"It wasn't long after I went up, he shouted 'there's an ambulance on the street'.
"That was surprising as this area is very quiet normally."