The Syrian government described on Thursday a Turkish offensive in Syria's Afrin region as an illegal "aggression" and said it would deal with it accordingly.

"The Turkish military operation in northern Syria is a blatant aggression," said a foreign ministry statement circulated on state media. The unauthorised presence of foreign forces represents "occupation and will be dealt with on this basis", it said.

Turkey launched an air and ground offensive last month against Kurdish fighters who control the northwest Syrian region of Afrin on the Turkish border, opening a new front in Syria's multi-sided war.