Spotlight: Syrian armed forces launch offensive on IS "capital," Mosul battle ahead of schedule

The Kurdish-led Syrian Democratic Forces (SDF) announced Sunday the start of an offensive on the Islamic State (IS) military group's de facto Syrian capital of al-Raqqa, while the military operation against the IS in Iraq's Mosul is ahead of schedule.

"The major battle to liberate al-Raqqa and its surroundings has begun," SDF spokesperson Jihan Sheikh Ahmed told a press conference held in Ain Issa, some 50 km north of the city.

Operation "Wrath of the Euphrates" under the air cover of the U.S.-led anti-terror coalition involves some 30,000 fighters and began on Saturday night, Ahmed said.

The SDF forces would first seize areas around al-Raqqa before taking the city, advancing on three fronts -- from Ain Issa and Tal Abyad to the north of al-Raqqa and from the village of Makman to the east.

The Syrian Observatory for Human Rights said the SDF has captured six villages in al-Raqqa and the U.S.-led airstrikes were targeting the IS positions in the north of the city.

"The fight will not be easy, and will require accurate and careful operations because the IS will defend its bastion desperately and it knows that the loss of al-Raqqa will mean it is finished in Syria," SDF spokesman Talal Sello told AFP.

Al-Raqqa and Mosul are the last major urban centers under IS control after the group suffered a string of territorial losses in Syria and Iraq over the past year.

Al-Raqqa, which was occupied by the IS in January 2014, is home to some of the group's top leaders and seen as the key to defeating the group militarily.

The city, with a population of 240,000 before 2011, has seen more than 80,000 leaving their homes and some of the IS' worst atrocities from stonings and beheadings to the trading of sex slaves over the past few years.

Meanwhile, U.S. Defense Secretary Ashton Carter also warned on Sunday that the fight to wrest control of al-Raqqa "will not be easy."

"As in Mosul, the fight will not be easy and there is hard work ahead, but it is necessary to end the fiction of the ISIL's caliphate and disrupt the group's ability to carry out terror attacks against the United States, our allies and our partners," he said, using an alternative name for the group.

"The international coalition will continue to do what we can to enable local forces in both Iraq and Syria to deliver ISIL the lasting defeat it deserves," Carter added.

Brett McGurk, U.S. special presidential envoy for the Global Coalition to Counter the IS, said Sunday in Jordan's capital Amman that there is no coordination with the Syrian regime or the Russians in the operation to retake al-Raqqa from the group.

Regarding the military action against the IS in Mosul, McGurk said it is the third week of the operation and "everything is ahead of schedule."

He added that days of Abu Bakr al-Baghdadi, the IS leader, are numbered and it is only a matter of time to eliminate him and his movement.

Iraqi security forces, along with Shiite and Kurdish militia, started an offensive on Mosul in October to retake the city, which fell to the IS group in 2014.

Aid groups have voiced concerns for civilians trapped in both Mosul and al-Raqqa, warning they may be used as human shields.

On Sunday, two bombings and a gunfire attack hit Iraq's Salahudin province, killing at least 43 people, including four Iranian pilgrims. Endi