Nine men have been arrested for planning to commit terrorist offences abroad, British police said on Saturday, adding that six of them were released without charge.
They were arrested on Friday night under the Terrorism Act near the city of Preston in Lancashire, northwest England, police said.
They were stopped on a highway near Preston as part of an intelligence-led operation by Lancashire Constabulary and the North West Counter Terrorism Unit.
Six of the arrested men were later released without charge, while three - aged 26, 29 and 36 - remain in custody. Police did not name the men.
Chief Superintendent Neil Smith said: "This is a very sensitive time for all our communities and we are working hard to ensure everyone is kept up to date with as much information as we can give.
"We will endeavour to carry out any searches as quickly as possible to minimise the impact on the area concerned. However, enquiries of this nature are complex and may take time to resolve."
Local media reports said police were searching five houses in the town of Burnley, about 40 km from Preston.
The Lancashire Evening Post said photographs of Friday night's incident on the highway show two vans surrounded by police vehicles. One van bears an image of the Palestinian flag on its side while the other has signs saying 'Stop Killing Children', 'Free Palestine', and 'From Blackburn (UK) to Gaza'.
It said the vehicles were travelling to join up with a convoy headed for Gaza.