A man and a woman have been arrested after a Liverpool clubber was stabbed to death while celebrating his 21st birthday.

Sam Cook was attacked after an argument broke out in the basement of the Empire nightclub in the city centre on Saturday night (21 October), said Merseyside Police.

The attack is understood to have taken place just before midnight in the four-storey club, which saw Cook rushed to hospital where he died just over an hour later.

A 20-year-old man from Anfield has been arrested on suspicion of murder and a 19-year-old woman was arrested on suspicion of assisting an offender, officers said today (23 October).

Both have been taken to a police station for questioning by detectives.

Officers are continuing their murder probe, which includes forensic enquiries and CCTV searches.

Cook died from a single stab wound to the heart, although police are still attempting to establish the murder weapon used.

It is unclear if his injury was caused by knife, or the jagged edge of a broken glass or bottle, according to the report in the Liverpool Echo.

Cook's devastated girlfriend, Lottie Owen, issued a plea on Twitter for any information that would lead to his attackers.

She said: "If anyone knows anything about the people who done [sic] this to my sam [sic] please get in touch with the police, took too young."

Detective Chief Inspector Mark Tivendale said: "Our investigation is in its very early stages but we initially believe that some kind of altercation may have taken place in the basement area of the bar, leading to a tragically fatal attack.

"We need to hear from anyone who witnessed an altercation, the incident itself, or may have seen, heard or come into contact with anyone involved.

"You may have heard words being exchanged or someone running from the bar. All information provided will be acted upon and may be vital in identifying who was responsible and bringing them to justice."

Empire nightclub was the scene of another stabbing on New Year's Eve, when bricklayer Callum Dunne, also 21, was stabbed in the thigh during a fight between two groups of men just outside the bar.

Dunne suffered a severed femoral artery and was found bleeding heavily by officers. He was given first aid in the street before paramedics arrived to take him to hospital in critical condition. He later recovered.