Baghdad, June 11 : Two Katyusha rockets were fired at the heavily fortified Green Zone in Baghdad, said a source from the Iraqi Interior Ministry. The attack took place before on Wednesday when the two rockets landed in the Green Zone, which houses some of the main Iraqi government offices and the US embassy, the source told Xinhua news agency. There were no immediate reports about casualties, but sirens were heard in the zone, the source said. No group has so far claimed responsibility for the attack, as the military bases housing US troops across Iraq and the American embassy have been frequently targeted by mortar and rocket attacks. The attack came as the Iraqi officials are preparing for a round of strategic dialogue with the US side on Thursday to discuss the relations between Baghdad and Washington as well as the future of the American forces in Iraq. The Iraq-US relations have witnessed a tension since January 3 when an American drone struck a convoy at Baghdad airport, which killed Qasem Soleimani, former commander of the Quds Force of Iran's Islamic Revolution Guards Corps, and Abu Mahdi al-Muhandis, deputy chief of Iraq's paramilitary Hashd Shaabi forces. The US airstrike prompted the Iraqi parliament on January 5 to pass a resolution requiring the government to end the presence of foreign forces in the country. More than 5,000 US troops have been deployed in Iraq to support the Iraqi forces in the battles against the Islamic State militants. /IANS