COPENHAGEN - Denmark said on Friday it would not extend a six-month mission for seven F-16 jets taking part in a US-led coalition focused on attacking Islamic State group targets in Syria and Iraq.

The decision came three days after the Pentagon said a September air strike in Syria by American, Australian, British and Danish planes - that reportedly killed some 90 regime forces, instead of IS fighters - was caused by a string of miscommunications, intelligence shortcomings and human errors.

"We have decided to withdraw the Danish fighter jets as planned," Danish Foreign Minister Anders Samuelsen told journalists after a meeting with parliament's Foreign Policy Committee.

"Instead of extending the mission we are sending an additional 20 to 21 troops," he said.

Defence Minister Claus Hjort Frederiksen said the new troops would bring engineering and construction skills to the operation.

"They will train Iraqi forces in, among other things, de-mining operations and will help our current contribution within training," he said in a statement.

In the second half of this year, Denmark has provided the coalition with seven F-16 warplanes - four of them operational at any one time - a C-130J transport aircraft and 400 military personnel, including 60 special forces troops.

The transport aircraft would also be withdrawn from the operation, the government said.

Denmark had seven F-16s in Iraq between October 2014 and October 2015, and in April this year lawmakers voted to expand its fight against IS into Syria.