AMSTERDAM (Reuters) - Seven men suspected of plotting an attack in the Netherlands with hand grenades, automatic weapons and explosives were ordered on Friday to remain in custody.

The men, aged 21 to 34, were detained after raids on four locations on Thursday that prosecutors said discovered grenades, firearms and explosives belts.

Three of the seven had previously been detained after attempting to join militant groups abroad. One was an Iraqi convicted in 2017 for trying to leave the Netherlands to join Islamic State insurgents.

On Friday, prosecutors said 100 kilograms of fertilizer had been found at the home of one the suspects, “possibly intended for a car bomb.”

“This network that has now been rolled up had the intention ... to carry out an attack on a public event with Kalashnikovs, and in another place, to cause a car bomb to explode,” Prime Minister Mark Rutte told reporters at a press conference in The Hague.

The suspects are only allowed contact with their lawyer, who has not made any public statement.

Police moved to arrest the men after months of investigation, following a tip from the country’s intelligence agency.