RIYADH (AFP) - Saudi Arabia's foreign minister on Thursday urged the US-led coalition conducting air strikes against the Islamic State in Iraq and Syria group (ISIS) to wage a ground war against the militants.

The kingdom, part of that coalition, "stresses the need to provide the military means needed to face this challenge on the ground," Prince Saud al-Faisal said at a news conference with US Secretary of State John Kerry.

Several Arab countries have joined the air campaign against ISIS.

President Barack Obama, anxious to avoid a drawn-out ground war, has backed an air campaign, but ruled out deploying infantry.

The Saudi minister also warned of Iran's growing role in Iraq, accusing the Shi'ite-dominated Islamic republic of "taking over" the kingdom's Arab neighbour through its aid in the fight against ISIS.

"Tikrit is a prime example of what we are worried about. Iran is taking over the country," Faisal said of the late Iraqi dictator Saddam Hussein's hometown.

The US military's top officer, General Martin Dempsey, said Tuesday that Iran's help in an Iraqi offensive to recapture Tikrit could be "a positive thing" providing it did not fuel added sectarianism.

On Thursday the United Nations said military operations aimed at retaking Tikrit from ISIS have caused about 28,000 people to flee their homes.

"We have urged all Iraqi forces to avoid and prevent the abuse to civilians of any kind of activity that violates international norms, fuels sectarian fears, and promotes sectarian divides, and that includes Iran in terms of their activities," Kerry said.

About 30,000 Iraqi security force members and allied fighters launched an operation to retake Tikrit on Monday.

Sunni-dominated Saudi Arabia is wary of the ambitions of its arch rival Iran across the Gulf.