Ukip leadership hopeful Steven Woolfe MEP has been hospitalised after collapsing in the European Parliament in Strasbourg today (6 October).
"[Woolfe] was taken suddenly ill in the European Parliament building in Strasbourg this morning. He has been taken to hospital in the city and he is undergoing tests," a Ukip spokesman said.
Woolfe, the party's migration spokesman, recently announced his bid to succeed Diane James MEP after she quit following 18 days into the job.
The 49-year-old's only current rival in the contest, Breitbart UK editor Raheem Kassam, has suspended his campaign in reaction to the news.
Former Ukip deputy chairman Suzanne Evans said she was "shocked" by the news and wished Woolfe a "speedy recovery".
Ukip's governing body, the National Executive Committee, is expected to meet next Monday (10 October) to decide on the rules and date of the latest leadership election.
Woolfe, an early favourite for the leadership last time out, was blocked from running in the race earlier this year because he submitted his application papers late.
UPDATE: 12:45 BST
The Daily Mail's European correspondent John Stevens has reported that there was an "altercation" that took place during a meeting of Ukip MEPs this morning.
Nigel Farage has described Woolfe's condition as "serious", while Sky News and The Telegraph say Woolfe has "bleeding on the brain". The party has 22 MEPs.
Patrick O'Flynn reportedly declined to discuss the incident. "My thoughts and prayers are with Steven and I'm desperately, anxiously waiting to hear further news," he told reporters. Meanwhile, images from ITV News have emerged of Woolfe face down on the floor.
"I deeply regret that following an altercation that took place at a meeting of Ukip MEPs this morning that Steven Woolfe subsequently collapsed and was taken to hospital. His condition is serious," Farage said in statement.
UPDATE: 13:51 BST
Sky News is reporting that Woolfe's condition is "life threatening".
UPDATE: 14:55 BST
Woolfe has now regained consciousness, the MEP is said to have had two "epileptic-like" fits and passed out. He said in statement: "The CT scan has shown that there is no blood clot in the brain. At the moment I am feeling brighter, happier and smiling as ever.
"As a precaution, I am being kept in overnight awaiting secondary tests to make sure everything is fine. I would like everyone to know that the parliamentary staff, the Ukip MEPs with me and hospital staff have been brilliant.
"Their care has been exceptional. I am sitting up, and said to be looking well. The only consequence at the moment is a bit of numbness on the left hand side of my face."
UPDATE: 20:37 BST
A spokeswoman for Mike Hookem, who was named as involved in the altercation, has denied that he had punched his colleague, insisting it had been a "verbal altercation", the Mail Online reported.
Meanwhile in a statement, Woolfe said the CT scan had shown that there is no blood clot in the brain.
"At the moment I am feeling brighter, happier, and smiling as ever. As a precaution, I am being kept in overnight awaiting secondary tests to make sure everything is fine.
"I would like everyone to know that the parliamentary staff, the Ukip MEPs with me and hospital staff have been brilliant. Their care has been exceptional. I am sitting up, and said to be looking well. The only consequence at the moment is a bit of numbness on the left hand side of my face."