UK police probe Manchester knifings as 'terrorist' attack

A British police probe into a triple stabbing at a Manchester railway station on New Year's Eve which injured three people is now being treated as "a terrorist investigation", the city's top officer said on Tuesday.

Counter-terrorism officials have arrested a man who remains in police custody, and are searching an address where he recently lived in the northwestern English city, Chief Constable Ian Hopkins said.

The suspect reportedly shouted "Allah" during what Hopkins called a "horrific attack" on three people, including a police officer, at Manchester Victoria station on Monday evening.

A man and a woman, both in their 50s, are still being treated in hospital after sustaining "serious" injuries, while the officer was also stabbed in the shoulder, he added.

"We are treating this as a terrorist investigation which is being led by counter-terrorism officers with support from Greater Manchester police," Hopkins told a briefing.

"They were working through the night to piece together the details of what happened and to identify the man who was arrested," he said, adding that an address in the Cheetham Hill area of the city was being searched.

Prime Minister Theresa May thanked emergency services for their "courageous response".

She wrote on Twitter: "My thoughts are with those who were injured in the suspected terrorist attack in Manchester last night."