Baghdad, March 2 (IANS): Iraqi security forces have launched a major offensive against Islamic State (IS) militants in the country's Salahudin province, a security source confirmed on Monday.

The offensive is aimed at recapturing key cities and towns seized by the IS terrorist group in the province in central north Iraq.

More than 30,000 Iraqi soldiers, policemen and allied Sunni and Shia militiamen are taking part in the offensive.

They launched the campaign from five routes: two from Mkesheifa and Sur Shnas south of Tikrit, the provincial capital about 170 km north of Baghdad, two others from Udheim and Tuz Khurmato east of Tikrit, and one more from Speicher airbase, just north of Tikrit, a provincial security source told Xinhua news agency on condition of anonymity.

The troops, backed by armoured vehicles and aircraft, have retaken control of several villages after heavy clashes with IS militants north of Samarra, some 120 km north of Baghdad, the source said.

Efforts were continuing to liberate Tikrit, the source said.

Late on Sunday, Prime Minister Haider al-Abadi, who serves as commander-in-chief of the Iraqi armed forces, announced the commencement of the offensive during a surprise visit to Samarra.

Abadi ordered troops and allied Sunni and Shia militias to avoid casualties among civilians and preserve their properties.

"The priority that we gave to the armed forces and all the forces fighting alongside with them is to preserve lives of citizens and to do their utmost to protect their properties," Abadi told reporters in Samarra.

The offensive comes after days of heavy shelling on IS positions in the targetted cities, towns and villages.

The military operations are designed to sweep all redoubts of IS militants across the province.