Police officers stand behind a cordon on Jeffery Street on Sept 19, 2017 in Newport, Wales. [Photo/VCG]

LONDON - A 25-year-old man was arrested on Tuesday in the Welsh city of Newport, becoming the third suspect to be arrested in connection with the Friday explosion at a subway station in west London, British police said.

Scotland Yard said that the man was arrested at about 7:08 pm local time on Tuesday. A building in the Welsh city was being searched, said the police.

The latest arrest was made after two other men aged 18 and 21 were arrested in connection with the bomb attack at Parsons Green subway station, which left 30 people injured.

A Scotland Yard spokesman said that the third man was arrested under section 41 of the Terrorism Act, which allows police to detain suspects without charge beyond the four days allowed for suspects connected to other crimes.

"The arrest was carried out by officers from the Met's Counter Terrorism Command, supported by colleagues from Gwent Police and the Welsh Extremism and Counter Terrorism Unit (WECTU)," the spokesman said.

Detectives were granted more time on Monday to question two young men held in raids over the Parsons Green station terrorist attack.

The Islamic State claimed responsibility for the fifth terrorist attack in the country over the past six months.

Previous attacks in London this year at Westminster Bridge, London Bridge and Finsbury Park as well as a blast at an Ariana Grande concert in Manchester killed dozens of people and injured more than 150.