Three men were arrested under the Terrorism Act at a UK airport after arriving in the country from Oman.
The men from Birmingham were arrested on Wednesday night on suspicion of possessing articles and documents with intent to use them for terrorist purposes overseas (contrary to Section 57 of the Terrorism Act 2000), West Midlands Police said in a statement.
All were detained at Heathrow Airport after arriving on a flight from Oman, the statement added.
Two of the men, aged 33 and 39, were from the Small Heath area of the city and the third, aged 33, from Alum Rock.
The arrests, made by officers from the West Midlands Counter Terrorism Unit, were pre-planned and intelligence-led.
They were not made in response to any immediate threat to public safety, the statement said.