Rotterdam police arrested a 30-year-old man who was found with an AK-47 Kalashnikov and two loaded magazines in his apartment, Dutch prosecutors said on Friday.

In addition to the gun and ammunition, authorities uncovered four boxes of highly explosive illegal fireworks. They also seized a painting in the man's apartment with a picture of the flag of the so-called "Islamic State" (IS) militant group.

Detectives searched the apartment after receiving a tip-off from intelligence agency AIVD, prosecutors said in a statement.

"He is suspected of preparing a terrorist crime," the prosecutors said, adding that the man was detained on Wednesday. Judges ordered the suspect remanded in custody.

Dutch broadcaster RTL reported that police uncovered mobile phones from the apartment as well as 1,600 euros ($1,687) in cash.

The investigation into the suspect was "still in full progress," said national prosecution spokesman Wim de Bruin.

"At this moment, we have only one suspect," he said, adding that he could not rule out the possibility of further arrests.

Netherlands on high alert

European intelligence officials have repeatedly warned of the threat posed by citizens returning from fighting alongside IS in Syria and Iraq. Since March 2013, the Netherlands' terrorism threat level has been set at one below its highest level - meaning that officials believe there is a realistic chance of attack.

Around 270 Dutch people are estimated to have left to join IS, while around 40 former fighters are known to have returned home from combat in Syria, the Dutch counter-terrorism agency said in a report last month.

Around 190 Dutch citizens, including women and children, are still located in Syria and Iraq, the report said.

After attacks by Islamist militants in France, Germany and Belgium, the Netherlands is considered a possible target due to its support of US-led military operations against IS.

Rotterdam, Europe's largest port, is home to a diverse population and one of the Netherlands' largest Muslim communities.

rs/se (AP, AFP, dpa, Reuters)