Baghdad:US Defence Secretary Ashton Carter on Monday arrived in the Iraqi capital of Baghdad on an unannounced visit to meet Iraqi leaders. Carter's visit comes as Iraqi forces are fighting against the Islamic State militant group and advancing to free the country's last major IS stronghold in Mosul, some 400 km north of Baghdad. Carter is expected to meet Iraqi leaders and top US military officials to discuss coordination of military campaign against the IS, and means to enhance US support by the international coalition to Iraqi forces fighting to free Mosul, Xinhua news agency reported. The visit came in less than three months after Carter's previous one in April when he discussed with Iraqi leaders America's offer to deploy extra troops as advisors to Iraqi forces. Hundreds of US marines are already in Iraq, serving as trainers and advisers, in an attempt to help the country win the battle against IS extremists in the province of Anbar as well as in northern Iraq. Iraq's security situation has drastically deteriorated since June 2014, when clashes broke out between Iraqi security forces and the IS militants. The IS took control of country's northern city of Mosul and later seized territories in Nineveh and other predominantly Sunni provinces. A US-led international coalition has been conducting air raids against IS targets in both Iraq and Syria. Many blame the current chronic instability, cycle of violence, and the emergence of extremist groups such as the IS on the US, which invaded Iraq in March 2003 under the pretext of seeking to destroy weapons of mass destruction. The war led to the ouster and eventual execution of former Iraqi President Saddam Hussein, but no WMD was ever found.