A forensics police officer works next women's shoes and a handbag on the ground behind a police cordon in Birstall near Leeds, June 16, 2016. Photo: Reuters

A British MP has died after she was shot and stabbed during an attack in her constituency, police have said.

Very concerned about reports Jo Cox has been injured. Our thoughts and prayers are with Jo and her family.

— David Cameron (@David_Cameron) June 16, 2016

Batley and Spen MP Jo Cox is seen in an undated handout image released on June 16, 2016. Reuters file photo

Media reports said Jo Cox, 41, Labour MP for Batley and Spen, was left bleeding on the ground by her attacker. A 77-year-old man also suffered slight injuries.

A 52-year-old man was arrested near Market Street, Birstall, West Yorkshire Police said. The MP held a weekly advice surgery nearby.

The MP's death was confirmed at police headquarters in Wakefield.

West Yorkshire Police said they were not looking for anyone else in connection with the attack.

Labour leader Jeremy Corbyn said the country would be "in shock at the horrific murder", describing the MP as a "much loved colleague".

"Very concerned about reports Jo Cox has been injured," Prime Minister David Cameron said on Twitter. "Our thoughts and prayers are with Jo and her family."

Follow: Live updates by BBC

READ MORE: Profile of Jo Cox by Sky News  

It's right that all campaigning has been stopped after the terrible attack on Jo Cox. I won't go ahead with tonight's rally in Gibraltar.

— David Cameron (@David_Cameron) June 16, 2016

"But for now, all our thoughts are with Jo's husband Brendan and their two young children. They will grow up without their mum, but can be immensely proud of what she did, what she achieved and what she stood for."

'People screaming'

Cafe owner Clarke Rothwell, who witnessed the attack, said he heard a "loud popping noise that sounded like a balloon burst - a loud balloon". 

"When I looked round there's a man stood there in his 50s with a white baseball cap on and a jacket with a gun, an old fashioned looking gun in his hand," he said.

"He shot this lady once and then he shot her again, he fell to the floor, leant over shot her once more in the face area. 

"Somebody tried to grab him, wrestling with him and then he wielded a knife, like a hunting knife, just started lunging at her with a knife half a dozen times. People were screaming and running from the area.

CAUGHT: Gunman who attacked British MP arrested via @mochachinnos https://t.co/W7vQIwTiza pic.twitter.com/wiVvWm3Q8Y

— Justin Miller (@justinjm1) June 16, 2016

British police said they had arrested a 52-year-old man after an attack which left a woman in a critical condition in Birstall, near Leeds in northern England, following media reports that a lawmaker had been attacked in the area.

"At 12.53 (1153 GMT) today, police were called to a report of an incident on Market Street, Birstall, where a woman in her 40s had suffered serious injuries and is in a critical condition," West Yorkshire Police said in a statement.

We have released a press release in response to the #Birstall incident. Read here: https://t.co/bhYH4XGx25

— WestYorkshire Police (@WestYorksPolice) June 16, 2016

"Armed officers attended and a 52-year-old man was arrested in the area. There are no further details at present," police added.