British media reported that Cox was seriously injured in the shooting, close to her constituency advice surgery in Birstall, near Leeds.

The UK’s Press Association news agency cited eyewitnesses who said Cox appeared to be involved in a struggle in the street with a man, whose gun went off twice. Cox was left bleeding on the pavement and another man was also injured.

Some reports suggest her attacker was also carrying a knife and may have stabbed Cox, who is MP for Batley and Spen.

Sky News quoted Labour party sources as saying that the 41-year-old mother of two was airlifted to hospital and her condition was said to be critical.

No motive was immediately given for the attack, but fellow Labour MP and shadow culture minister Maria Eagle tweeted that the attacker had shouted “Britain First,” the name of a far-right, nationalist party and movement. The claim was made by several witnesses at the scene, British media reported.

The attack took place in Birstall, near the northern city of Leeds

Police say a 52-year-old man has been arrested following the incident, which took place at around 1 p.m. local time (12:00 UTC).

On Twitter, British Prime Minister David Cameron said “our thoughts and prayers are with Jo and her family,” while Labour leader Jeremy Corbyn said he was “utterly shocked” at the shooting.

Cox was elected to Britain’s parliament in 2015 after a career as an aid worker for Oxfam. Part of her constituency – the town of Batley – is among the poorest in the country, part of an EU transformation zone, and has a high immigrant population.

Following the attack, both the pro and anti-European Union camps have suspended their campaigns, with just a week to go until Britons vote on their country’s membership of the bloc.

Cameron tweeted that he wouldn’t travel to Gibraltar for a campaign rally on Thursday evening.