Iraq launched an air strike on a gathering of Islamic State (IS) militants in neighbouring Syria, killing members of the hardline militant group who planned cross-border attacks, its military said on Thursday.

F-16 fighter jets bombed and destroyed an "operations room" where the militants were meeting. IS, which once occupied a third of Iraq's territory, has been largely defeated in the country but still poses a threat along its border with Syria.

"According to intelligence, those terrorists who were killed were planning criminal operations using suicide vests and intended to target innocents in the next few days inside Iraq," the military said in a statement.

The Iraqi military has carried out several air strikes against IS in Syria since last year, with the approval of President Bashar al-Assad and the U.S.-led coalition fighting the militants.

Iraq has good relations with Iran and Russia, Assad's main backers in the Syrian war, and also enjoys strong support from the U.S.-led coalition.

Prime Minister Haider al-Abadi declared final victory over IS in December but the group still operates from pockets along the border with Syria and in a rugged mountainous area in northeastern Iraq.

It has continued to carry out ambushes, killings, and bombings across Iraq since it abandoned its goal of creating a self-sufficient caliphate straddling Iraq and Syria.