Danish troops fighting in Iraq will now be able to cross into Syria as part of the US-led coalition against the Islamic State group, officials said on Friday.

The defence ministry said in a statement that Denmark's parliament had authorised special operations soldiers "to perform their tasks in the Iraqi-Syrian border area".

"The fight against ISIL (Islamic State) is an important foreign and security policy priority for the government," Danish Foreign Minister Anders Samuelsen told the Ritzau news agency after parliamentary discussions in Copenhagen.

Samuelsen said the coalition had asked Denmark, a NATO member, to send troops to Syria, but he did not reveal how many or where they would be deployed in the war-torn country, nor when.

"The government has, therefore, based on a specific request from the coalition, decided to expand the functions of special operations forces in Iraq and Syria," Samuelsen said in remarks quoted by public broadcaster TV2.

Denmark has so far provided the coalition with 400 military personnel, including 60 special forces troops, as well as seven F-16 warplanes -- four of them operational at any one time -- and a C-130J transport plane.

The parliament's authorisation applies to special ops forces already included in that number, but it was not clear how many or whether further troops would be drafted in.

Last month, these troops were given a mandate to open fire if they or their Iraqi allies were fired upon, which raised concerns among Danish officials about the risk of escalating the violence.

Denmark's decision comes more than a month after it said in December that it would not extend a six-month mission for its seven F-16 jets taking part in the coalition.