Three men have been arrested in the Danish capital on suspicion of plotting a "terror act", Denmark's intelligence services have said.

Intelligence officials said police found the three men in possession of automatic firearms and ammunition.

The Security and Intelligence Service, or PET, said the men were arrested in two separate locations in Copenhagen in connection with an ongoing terror investigation.

Aside from facing preliminary charges of possessing illegal firearms, PET also said they were "suspected of having been in the process of preparing a terrorist act," but did not give any details about the target of such an attack.

"The investigation will establish on whether possible terror threats have been addressed and averted by the arrests," it said. Preliminary charges are a step short of formal charges.

PET described the men as a 22-year-old Jordanian national, a 23-year-old Turkish man living in Denmark and a 21-year-old Danish national who usually lives in Egypt.

The men face a custody hearing on Saturday, said Svend Foldager, a Copenhagen police spokesman.

PET would not say if it suspects the men of belonging to a specific group, AP news agency reported.

'No trial links'

Speaking to Al Jazeera from Copenhagen, Thomas Norman Hougaard, a journalist from the Danish Broadcasting Corporation, said that the suspects had been arrested on Friday morning.

He said that while an important trial, which began two weeks ago of four men after the 2005 publishing of 12 caricatures of Prophet Muhammad, was ongoing in the country on Friday, this had not been linked by the authorities to the arrests.

There has been no information about possible plans of attacking newspapers that published the cartoons, Hougaard said.

The four men, all residents of Sweden, are on trial for plotting a shooting spree in December 2010 against Jyllands-Posten's Copenhagen office.

The publication of the cartoons by the newspaper in 2005 set off a wave of violent protests and ignited a debate over freedom of the press and respect for religion around the world.

Source: Al Jazeera and agencies