Five people have been arrested on suspicion of being involved in the commission, preparation or instigation of acts of terrorism.
Four people - three men aged 26, 40 and 59 and a 29-year-old woman - were arrested in Birmingham on Thursday night, while a 26-year-old man was arrested at Gatwick Airport early on Friday morning.
Assistant Chief Constable Marcus Beale, who leads on counter-terrorism for the West Midlands, said: "This action forms part of an extensive investigation by West Midlands Counter Terrorism Unit (WMCTU), together with the wider counter-terrorism network, MI5 and international partners including Belgian and French authorities to address any associated threat to the UK following the attacks in Europe.
"The arrests were pre-planned and intelligence-led. There was no risk to the public at any time and there is no information to suggest an attack in the UK was being planned."
The five suspects are being held in the West Midlands, where they are being questioned by WMCTU officers.
Police are also searching a number of properties in Birmingham as part of the investigation.