The arrests came after a series of raids in Sydney's southwest on Tuesday morning.

The men first came to the attention of detectives who were investigating possible terrorism funding in NSW under Strikeforce DeHaar.

A 38-year-old and a 39-year-old were arrested at a Sydney Olympic Park cafe after 8am on Tuesday and taken to local police stations.

Later 19 search warrants were executed in Sydney's southwest at homes, businesses and storage units, leading to a further six arrests. Those men were aged between 27 and 42.

The eight accused men are expected to be charged with various offences, NSW police said in a statement.

Detectives allege the group distributed more than seven tonnes of tobacco products worth more than $1.8 million.

The group also facilitated the importation of 475,000 packets of cigarettes - which would have accrued $9 million in excise if imported legally - and laundered more than $1.2 million in the proceeds of crime, police say.

Assistant Commissioner Mick Willing assured the public there was no current or impending terror threat from the crime syndicate's activities.

"The terrorism funding aspect (of the investigation) is ongoing," he told reporters.

"(But) it's quite clear and it's well known around the world (that) the nexus between organised crime and terrorism is strong and alive."

Mr Willing said police believe they'd arrested the mastermind of the syndicate as well as those intricately involved mid-level.

The men will face a number of charges such as money laundering, directing and participating in a criminal group, dealing with the proceeds of crime and tobacco smuggling.

Australian Associated Press