DHAKA: A military operation to retake the Iraqi city of Tikrit from Islamic State (IS) has caused about 28,000 people to flee their homes.

Those displaced are headed towards the city of Samarra, the UN said, but many families are stranded at checkpoints.

Aid convoys carrying relief supplies are being sent to the area by UN agencies to help those affected, reports the BBC.

The operation to retake Tikrit involved some 30,000 soldiers and Shia militiamen.

They are trying to encircle the IS fighters, but their advance has been slow due to the roadside bombs and booby traps planted since the city was overrun last June.

Iraqi jets and helicopters are supporting the ground troops but US-led coalition aircraft are not involved.

Militants also set fire to oil wells outside the city on Thursday, officials said, creating clouds of smoke in an apparent bid to obscure targets from air strikes.

BDST: 1400 HRS, MAR 06, 2015