Sweden has suspended all flights to northern Iraq because of concerns about increased military activity in the area, the country's transport agency said on Friday.

Iraq closed its northern airspace for at least 48 hours earlier this week because of military traffic from Russia's air campaign in neighbouring Syria.

Commercial routes from the Middle East and Europe were disrupted, as were reconnaissance and resupply flights for the US-led coalition that has been bombing Islamic State targets in Iraq and Syria for more than a year, separately from the Russian campaign.

Flights had resumed in northern Iraq by Wednesday, but Sweden's transport agency said in a statement on its website it was limiting Iraqi Airways and Air Zagros from flying to Erbil and Sulaimaniya starting on Saturday.

A representative for Air Zagros, operated by a subsidiary of Turkey's AtlasGlobal, confirmed a weekly connection between Stockholm and Erbil had been suspended until further notice.

Iraqi Airways could not immediately be reached for comment.

The transport agency's statement said other flights between Sweden and northern Iraq, including those operated by German airline Germania, had also been cancelled.

"We understand that our decisions affect those travellers who can no longer fly to and from northern Iraq. But we have to put passenger safety first," said Simon Posluk, head of the transport agency's shipping and aviation facilities.

Russia began launching missiles and long-range bombers at targets in Syria from warships in the Caspian Sea last month. They travel some 1,500 km (900 miles) over Iran and Iraq.

An aviation official in Erbil previously said a change in the missiles' route had brought them "uncomfortably close" to the airport, which serves the semi-autonomous Kurdistan region along with the one in Sulaimaniya.

Moscow says its air strikes were requested by Syrian President Bashar al-Assad and contends their main target is Islamic State militants who control large swathes of Syria and Iraq. But it has been accused of hitting other targets, including territory occupied by Western-backed rebels opposed to Assad.

With competing military demands on the airspace over Iraq and Syria, flight time and fuel costs for commercial traffic has risen as aircraft queue to enter narrow corridors. – Reuters