LONDON, Dec. 30 -- A 21-year-old man has become the fifth arrested as part of an investigation into a potential Christmas terror attack in Britain, police said Saturday.

The latest arrest was been made in South Yorkshire as a result of an ongoing investigation led by Counter Terrorism Policing North East.

The 21-year-old man, from the Fir Vale area of Sheffield, was arrested in an intelligence-led operation on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism.

Police swooped on the Firth Park area of Sheffield at approximately 11 p.m. on Friday evening with two addresses, a residential address in Fir Vale and a business address in Firth Park, currently being searched by officers.

As part of the same ongoing investigation, two men appeared before Westminster Magistrates in London on Friday charged with terrorism offences. They were among the four men arrested on December 19 in Sheffield and Chesterfield.

Farhad Salah, 22 and Andi Sami Star, 31, were both remanded to the Old Bailey court in London, charged with engaging in the preparation of an act of terrorism.

One of the four arrested on December 19, a 36-year-old man from Sheffield remains in custody while a 41-year-old man, also from Sheffield, has been released without charge.

South Yorkshire Police Deputy Chief Constable Mark Roberts said: "I understand that this activity will cause concern, especially as there has been similar activity in recent weeks. I would like to firmly reiterate that we continue to work closely with our colleagues in Counter Terrorism Policing North East to keep our communities safe and identify threat and risk. Our main priority is public safety and protecting the people of South Yorkshire."