Police are searching for one suspect following a series of stabbings in Birmingham city centre in which one man was killed and seven other people injured.

West Midlands Police declared a major incident after officers were called to reports of a knife attack in the early hours of Sunday, with further stabbings then being reported.

Announcing the launch of a murder investigation, the force said in statement: “A man has tragically died. Another man and a woman have suffered serious injuries and five others have also been injured, although their injuries are not thought to be life-threatening.”

Chief Superintendent Steve Graham said there is “absolutely no suggestion” that the stabbings were “terror-related”, with the attacks on victims appearing to be “random”.

He told a press conference that officers are treating four incidents in Constitution Hill, Livery Street, Irving Street and Hurst Street as linked, with the suspect moving from north to south.

He said no arrests have been made and police are looking for one male suspect, with “significant resources” being put into tracing him.

Birmingham stabbingsPolice officers at a cordon in Hurst Street in Birmingham after one man was killed and seven other people injured in a series of stabbings (Jacob King/PA)

“Already we’ve got people going down drains, we’ve got that level of detailed searches taking place which will hopefully reassure the people that we are doing everything we can do to trace the offender,” said Mr Graham.

He added that a number of descriptions had come in of the suspect but police are not releasing any details at this time and asked the public to come forward with any information or footage they may have.

Mr Graham said there is no known connection between the victims in the four linked incidents and that extra officers have been deployed in Birmingham.

Two people who were critically injured are still being treated, he said.

He added that there is “absolutely no suggestion” that guns were involved in the incident, and there is no evidence that it was motivated by hate towards any particular group, nor gang-related.

Mr Graham also said there is no evidence to show that it was related to “people squabbling over tables” in the city centre.

On Twitter, Prime Minister Boris Johnson thanked the emergency services.

He tweeted: “All my thoughts are with those affected by the terrible incident in Birmingham last night.”

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Home Secretary Priti Patel also said “all her thoughts” were with people affected by the “shocking incident” in the city.

“Our emergency services are working hard to find whoever is responsible and bring them to justice,” she tweeted.

West Midlands Ambulance Service (WMAS) said it sent a large number of resources in response to the stabbings, including 14 ambulances.

A team of St John Ambulance volunteers at the SafeSpace project at the Arcadian venue were also involved in treating casualties.

Seven patients were treated by ambulance staff – five of whom were taken to the major trauma centre at Queen Elizabeth Hospital Birmingham.

Three of the five taken to the major trauma centre had critical injuries and one man was pronounced dead shortly after arrival, WMAS said.

The ambulance service said an eighth patient with minor injuries did not receive ambulance treatment.

West Midlands Police said the incidents took place between 12.30am and 2.20am.

The force said officers are still at scenes across the city, including Livery Street, Irving Street and Hurst Street.

Forensic officers could be seen searching streets in the city centre on Sunday morning.

Mr Graham said in an earlier statement: “The events during the early hours of this morning are tragic, shocking and understandably frightening.

“Please be assured that we are doing absolutely everything we can to find whoever was responsible and try to understand what exactly happened.”