The Iraqi army and Shi'ite militiamen have been engaged in fierce battles with Islamic State (IS) fighters in Tikrit, as they attempted to recapture the Iraqi city.
Whilst US airstrikes have not been reported to have been deployed, the Iraqi air force conducted several strikes since the offensive was launched on Sunday.
Reuters reported that Iranian military commander Qassem Soleimani was at the battlefront. The commander had been assisting to co-ordinate Iraqi counter-offensives against IS, but Moeen al-Kadhimi, a leader of the Shi’ite militia known as the Popular Mobilisation force, told the BBC that the role he was playing was minimal.
“We receive our orders and instructions from the Iraqi military leadership, but we make use of the advice of the foreign advisers," said Mr Kadhimi.
He went on to add that several roadside bombs had slowed progress into the city.
"We're not in a rush to end the Tikrit operation," he said. "We're very careful in our planning, especially because the IS military strategy is based on planting explosive devices on the roads, in houses, everything... even lampposts."