Malaysian police said Friday they detained three men, including two foreigners, for questioning over their possible involvement in terrorism after the U.S. and Australian embassies warned of a potential attack at a popular hawker street in Kuala Lumpur.

A Malaysian, an Indonesian and a Syrian, aged between 30 and 51 years, were picked up Thursday as part of an ongoing counterterrorism operation, said national deputy police chief Noor Rashid Ibrahim.

He said one of them often visited Yemen and entered Malaysia a few days ago. No details were given about the others.

"Investigation is ongoing to determine if the three of them are involved in any plans to launch attacks in Malaysia," he said in a statement.

Police beefed up security in popular public places and other strategic locations, he added.

The U.S. Embassy issued an advisory Thursday saying it has credible threat information of a possible terror acttack and urged its citizens to avoid Alor Street, located in a shopping belt in the city center, and its immediate surrounding areas.

It said that terrorist organizations had in the past planned attacks to coincide with significant dates, but gave no details.

The Australian Embassy issued a similar alert to its citizens based on the U.S. warning.

Malaysia has arrested more than 100 supporters of the Islamic State group in the past two years, some of whom were allegedly plotting attacks in the country. They included civil servants and members of security forces.

Police said they were held for offenses such as raising funds for the militants, recruiting Malaysians and getting weapons for attacks targeting Kuala Lumpur and other strategic locations. No attacks have occurred in Malaysia.