Iraqi Airways has resumed commercial flights between the central Iraqi province of Najaf and Iranian airports, according to the country's state-run Iraqi News Agency.

The flights restarted on Monday after Najaf and three other Iraqi airports had temporarily suspended services. The suspensions were driven by fears of secondary sanctions imposed by the United States targeting aviation services linked to Iran.

The resumption allows Iraq's flag carrier to bypass disputes with international contractors whose concerns over secondary penalties had halted ground handling services for flights connected to Tehran.

Earlier the same day, Iran filed a formal complaint with the International Civil Aviation Organization (ICAO) over the US aviation sanctions, according to Iranian state media.

Iran's Civil Aviation Organisation chief Abuzar Shiroudi said coordinated efforts are underway with Iran's Foreign Ministry to resume flights through legal channels. He also stated that the ICAO had ruled in Iran's favour regarding its formal protest over the US measures.

Shiroudi additionally said Tehran had filed a complaint with the International Court of Justice in The Hague over attacks on airports, aircraft and radar systems. The case remains under review, and any compensation will depend on the court's final ruling, he added.

Iran's civil aviation chief said Tehran is also seeking explanations from several countries through diplomatic channels regarding halted flight routes.

US sanctions on Iranian airlines came into force on September 23, placing foreign airports and companies that service sanctioned Iranian carriers at risk of secondary penalties. The measures have not grounded Iranian aviation entirely.

According to reports, the chief executive of Tehran's Imam Khomeini International Airport said flights to East Asia are operating without cancellations.

Airports in Azerbaijan, Georgia, Iraq, Oman and the United Arab Emirates have recently cancelled flights operated by Iranian airlines.