A sailor is the prime suspect in the murder of a young Icelandic woman whose case has gripped the nation, police have told The Independent.

Birna Brjánsdóttir's body was found washed up on the coast of the country shortly after she went missing in the early hours of 15 January

Wearing her Doctor Martin boots, the 20-year-old was alone when she left a nightclub in the country's capital Reykjavik and walked up the high street to buy a kebab.

Awaking several hours later, her parents discovered she had failed to return home.

As 800 people volunteered to help look for her - the biggest search and rescue mission in Iceland’s history - the case gripped the nation.

A week later, her body was found swept up on a beach 35 miles south the capital. Within hours of its discovery, candlelit vigils were held in both Iceland and Greenland. Last weekend, more than 8,000 people took part in a march through the streets of Reykjavik in memory of Ms Brjánsdóttir.

Two sailors from Greenland aged 25 and 30, whose boat had been docked on the same beach, were arrested in connection with her disappearance.

Police told The Independent that the 30-year-old has now been release. But the second suspect will be held in isolation for a further two weeks.

He is thought to have "gone off" with Ms Brjánsdóttir after his friend returned to the boat and, four hours later, boarded the vessel without her.

Volunteer rescuers search for clues relating to Ms Brjánsdóttir's murder during the biggest rescue and search operation in Iceland's history (Icelandic Association for Search and Rescue)

Einar Gudberg Jonsson, the detective chief inspector (DCI) in charge of the case, told The Independent: “A man was released last week after we were satisfied that wasn’t involved in the death of Birna, and that he wasn't in the car when it happened. We prolonged the second suspect’s time in custody last week.

“We haven’t yet had the final report from the medical examiner, but it appears Birna got into the car with these men on the high street, meaning it was her and the two men in the vehicle."

He added that they drove to the port area of Hallgrimskirkja, where their ship was docked.

"One of the men, very drunk, left the car and got on board the ship," said DCI Jonsson. "Birna and the other man then go off, and we have a four-hour gap where we can’t plot the route or where they went.

"The man later comes back without Birna, and we see him on CCTV at the docks cleaning the car. He then returns it to the car rental and boards the boat, which leaves the harbour that evening."

Reports in Icelandic media suggest Ms Brjánsdóttir drowned, saying her autopsy reveals she had water in her lungs, indicating she was still alive when she was dumped into the ocean.

DCI Jonsson could not confirm this. While the police had seen the findings of the autopsy, they were unable to discuss them in public at this point, he said.

In a country with no armed police on the streets, no army and the world’s third-lowest murder rate, the murder case of Ms Brjánsdóttir is unprecedented.

“This kind of thing has never happened. In the whole of the Iceland there are around two murders a year,” said DCI Jonsson.

“We’ve had some disappearances of people here, but nothing of this sort where a stranger picks up another total stranger, drives off and does something and then kills the person and dumps the body in the ocean. That’s not something that happens here.”

He added that the Icelandic population was “devastated”, but that there had been no animosity towards Greenland, despite it being the suspect’s country of origin.

“Everybody here is devastated. There have been a lot of talks and a lot of media coverage and a lot of speculation and anger,” DCI Jonsson said.