Two men were arrested today as part of an on-going terrorism investigation, police said.
The men, aged 40 and 25, were arrested under the Terrorism Act 2000 at an address in Alva, Clackmannanshire.
Shopkeeper's son Mohammed Siddique, 20, was arrested in the same town on Thursday April 13, as part of the same investigation.
Central Scotland officers also said they were searching a property today in Bridge of Allan, Stirlingshire - around seven miles from Alva.
Police said the arrests were part of a continuing "major" inquiry under the Terrorism Act 2000.
A statement said: "The men, aged 40 and 25, were arrested at an address in Alva, Clackmannanshire, earlier today.
"Their arrest follows that of a 20-year-old man in Alva, Clackmannanshire, on Thursday April 13.
"In addition, an address in Bridge of Allan is being searched in connection with the inquiry."
The statement added: "This is a major ongoing inquiry. However, there remains nothing to suggest a direct threat to communities, the threat levels to the UK remain unchanged and an extensive reassurance strategy is in operation."
Amy McEwan, 22, who works at The Coffee Pot cafe in Bridge of Allan, said the police operation in the town centred on an address in Union Street.
She said the house was occupied by an Asian family.
A caretaker at the Allan Community Centre said he saw a police presence in Union Street at 10am today, which included two people in white forensic suits.
He said: "There were flashing lights outside a property.
"I saw two people in white forensic-style suits getting into a car."
A yellow-painted house in Union Street was at the centre of the police operation.
By mid-morning, two uniformed police officers were standing guard outside and police tapes cordoned off the area.
Nearby was a parked police van, with white-clad investigators visible inside it.
BBC Scotland reporter Duncan Kirkhope, who witnessed part of the Bridge of Allan operation, described seeing "a sea of police and vehicles".
He told the BBC Scotland news website he was driving through the town's main street with his son just before 9.30am when he saw police blocking off Union Street.
He said: "I looked down the street and all I could see was a sea of police and vehicles - mainly uniformed officers and marked police cars.
"By the time we got parked and walked round, a number of the marked vehicles drove away and then we saw people being driven away from the semi-detached house in unmarked police cars.
"One unmarked car had three Asian people in the back, possibly two women and a young person, or a woman and two young people."
He said the other car had one Asian male, possibly in his 50s, in the back seat.