Talks are under way to free a Dutch helicopter crew captured in Libya trying to evacuate foreign citizens, the Netherlands' defence ministry says.
The three marines landed their Lynx near the port of Sirte on Sunday, flying in from the Dutch warship Tromp, which is anchored off the Libyan coast.
"Intensive negotiations" were under way, a ministry spokesman said.
The ministry was in contact with the marines who were "doing well under the circumstances", he added.
"We hope they will be released as quickly as possible," Otte Beeksma told the Associated Press news agency.
Asked if the Dutch government considered the marines hostages, he replied: "They are being held by Libyan authorities."
Two people the marines were trying to rescue - one Dutch person and another European - were captured but have since been released and have left Libya, Dutch media say.
"It was a consular evacuation," Mr Beeksma added.
"During the operation the helicopter was grounded by an armed unit."
'A real risk'
Dutch Prime Minister Mark Rutte said news of the men's capture had been kept quiet to assist talks on their release.
"These are situations that benefit from total secrecy because then you can carry out discussions in peace to ensure these people get home safely," he told Dutch news broadcaster NOS.
"It is terrible for the crew of the Lynx helicopter. Everything is being done to make sure the crew gets home."
The Tromp, which was initially to have taken part in an anti-piracy operation off Somalia, headed for the Libyan coast on 24 February.
The port city of Sirte is considered the main remaining stronghold of Libyan leader Muammar Gaddafi in the centre of the country, as he struggles with a spreading revolt against his rule.
Military historian Christ Klep says he is surprised by the Dutch action because of the dangers of landing near Sirte.
"It seems to suggest it may have been a diplomat, for instance, or somebody of special importance anyway," he told Radio Netherlands Worldwide.
"I would have thought you would want to avoid stirring things up in Libya and not attract attention to yourself.
"There must have been a reason they were prepared to take this extra risk and it was a real risk because it's essentially impossible to defend one of those Lynx helicopters."