A woman is in a critical condition after being stabbed in the neck in an “unprovoked attack” in Birmingham city centre.

A man in his 20s has been arrested on suspicion of attempted murder after the attack on Friday night.

It happened on Smallbrook Queensway, just outside the Bullring shopping centre and opposite the main entrance to New Street railway station, shortly before 21:00 GMT.

A woman in her 30s suffered a serious neck injury and is in hospital in a critical condition, West Midlands Police said.

The force said a man was arrested close to the scene and remained in custody.

Officers are currently carrying out inquiries near the scene, which is in an extremely busy part of the city centre near to the Bullring.

A police tent remains on the pavement, just outside the shopping centre and opposite the main entrance to New Street.

“We believe this was an unprovoked attack and are working to understand why it happened,” said Det Insp James Nix.

“We will have officers in the area today to continue our investigation and provide reassurance.

“We are not currently looking for anyone else in connection with this incident.”

Shalini Doal, who works nearby, said she saw the scene when she left work at about 22:00.

“They’d blocked off all the roads, a lot of people were walking past just wondering what had gone on, it was quite a chaotic scene,” she said.

“A few of my colleagues had their breaks around the time of the incident, and said they heard a commotion outside, around 9 o’clock.”

She said the attack was concerning because she and her colleagues often finished their shifts as late as midnight or 01:00.

“A lot of my colleagues take public transport, take the tram… our safety is at risk essentially, here in the city centre,” she added.

Ashley Birks, 25, from Stoke-on-Trent, said he comes to Birmingham fairly regularly to see his girlfriend who lives in the city and was concerned about what had happened.

“It makes me worried for my girlfriend.

“She doesn’t drive and works at all of the big music venues… and to think something completely unprovoked (happened), you know, it’s horrible,” he said.

The force has appealed for witnesses, and urged anyone who knows more to contact 101.

St Martin’s Queensway westbound has been closed from Moor Street Queensway to Smallbrook Queensway.

Buses are being diverted on to Moor Street.

The cordon is expected to be in place all day, the BBC has been told.

Additional reporting by Amy Cole, Midlands Today and Yasmin Malik, Newsbeat