The men – three aged 19 and one aged 24 – stand accused of raising funds for terrorism and travelling to Pakistan to receive terrorist training.

The West Midlands Counter Terrorism Unit arrested the men at their home addresses early this morning.

A spokesman for West Midlands Police said the arrests were “pre-planned” and armed officers were not involved.

The arrests appear to be a part of Operation Pitsford, an inquiry which has seen eight people arrested and charged over the past two months in connection with terrorist plots. Three are alleged to have been plotting a suicide bombing campaign of “mass murder” across Britain.

The four men arrested today are being held under the Terrorism Act 2000. Detectives have 48 hours to question the suspects before deciding whether to charge them, and have the option to apply for a warrant for further detention.

Several of those arrested as part of Operation Pitsford have been accused of travelling to Pakistan to learn bomb making, how to use weapons and poison making.