The U.S. military top officer arrived in Baghdad Monday to discuss military cooperation as Iraqi forces freed the town of al-Alam in the Salahudin province from the Islamic State (IS) militant group.

General Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff arrived in Baghdad and was briefed by Iraqi military officers about the development of the anti-IS offensive.

Dempsey met with Iraqi Defense Minister Khaled al-Obeidi, with the two later appearing in a joint press conference, during which Obeidi downplayed U.S. concerns about the growing Iranian role in combatting IS militants.

"We are in a state of war and there is a balanced U.S. and Iranian munitions and intelligence aid to Iraqi forces," Obeidi said.

"We deal with world states, whether America or Iran. When Daash (IS militant group) captured a few Iraqi cities, the army situation was critical, so we asked for help from friends," Obeidi added.

Washington is worried about the leading role of Iran, which is not part of the U.S.-led coalition in fighting the IS group.

The neighboring Shiite state of Iran has close ties with the Iraqi Shiite-led government.

Iran's growing role in supporting the Iraqi Shiite militias in battles against IS in the Sunni areas has increased fears among Sunni Arab tribes in Salahudin province of possible retaliation by Shiite militias, thinking that sons of Sunni tribes collaborated with IS extremist militants in killing hundreds of Shiite soldiers during the Iraqi forces withdrawal before the IS advance on June 12 of last year.

Meanwhile, when Dempsey was asked if the United States would use air power to stop IS from destroying Iraqi antiquities, he said it's possible for air power to defend Iraqi heritage sites, but they must be "very precise" to avoid civilian casualties, as Washington does not want to create additional hardship while it targets IS militants in Iraq.

Dempsey is also scheduled to meet with Iraqi Prime Minister Haider al-Abadi and senior U.S. officials during his visit to Baghdad.

Iraqi ground forces and allied Shiite and Sunni militias, supported by armored vehicles and covered by Iraqi aircraft, entered the town of al-Alam east of Salahudin's provincial capital city of Tikrit from the south and the east after recapturing several outlying villages following clashes with IS militants.

Sporadic clashes are still underway inside the town as IS militants continue to fight on the western side of the town, the source said, adding that explosive experts started defusing dozens of roadside bombs and booby-trapped buildings.

Meanwhile, Iraqi forces started clearing roadside bombs on roads leading to outer neighborhoods of Tikrit, as heavy clashes and shelling continued targeting IS sites inside the city, the source said.

Also in the province, troops and allied Shiite militias arrived at Ajil oilfield east of Tikrit following days of clashes with IS militants, the source said.

Earlier on Thursday, IS militants apparently set fire to oil installations as flames and plumes of black smoke rose above the area, the source added.

The small Ajil oilfield is one of the most important financial resources in funding IS militants which extracts about 10,000 barrels per day and relays them by 300 tanker trucks to the Nineveh province and IS-held areas in Syria.

Some 30,000 Iraqi forces and thousands of allied Shiite and Sunni militias were involved in a week-long offensive to recapture Tikrit and other key towns in the north of the province from IS militants.

Elsewhere, Kurdish security forces, known as Peshmerga, supported by U.S.-led coalition aircraft, carried out an offensive against IS sites in western and southern parts of Iraq's northern province of Kirkuk.

The Peshmerga seized several villages and advanced to free the militant-held town of al-Ryadh, in the southwest of the capital city of Kirkuk, 250 km north of Baghdad, a Kurdish security source anonymously informed Xinhua.

In addition, U.S.-led coalition warplanes carried out airstrikes supportive of the Peshmerga forces and pounded IS positions in southwest Kirkuk, destroying 29 vehicles, eight shovel trucks and killing 180 militants, according to the source.

The extremist IS group seized vast amounts of territory in northern Iraq since June 2014 and announced the establishment of a Caliphate in areas under its control in Syria and Iraq.

The United States built an international coalition which includes countries in and outside the Middle East, to check IS expansion, carrying out airstrikes against the armed group in both Iraq and Syria.