Baghdad, Iraq - Iraqi security forces have taken the lion's share of the credit for seizing Tikrit from the Islamic State of Iraq and the Levant (ISIL), following the refusal of major Shia militias to participate in the fighting due to US involvement.

Tikrit was one of the biggest Iraqi cities taken by ISIL last summer, when the armed group swept through majority-Sunni areas in northern and western Iraq.

On Monday, Iraqi Prime Minister Haider al-Abbadi announced that Iraqi security forces, backed by small militia groups, gained control of Tikrit and drove away ISIL fighters. 

The Iraqi Federal Police and special forces, an elite force of the Iraqi army, called the Golden Division, were the main combatants against ISIL in the battle of Tikrit, according to senior federal police and interior ministry officials.

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Only a few elements of the popular mobilisation forces - an alliance of mainly Shia militias and multi-sect volunteers formed last June after the failure of the Iraqi army to stop ISIL - took part.

Most of the well-equipped and better organised Shia militias refused to join the final stages of the battle of Tikrit as long as the US air force was striking the city.

"Despite our pride and appreciation for all of our armed forces and the popular mobilisation [fighters] which took part in this battle, today we have to say that the federal police troops ... were the main force that has been in the front-line and the spearhead to finish off Daesh [ISIL]," Mohammed al-Ghaban, Iraq's interior minister, said in an interview broadcast on Monday by state TV.

In a televised press conference with Iraqi ambassadors, Prime Minister Abbadi announced the liberation of Tikrit and thanked all the troops that took part - including the US-led international coalition, which launched 28 air strikes against ISIL in Tikrit over the past three days, according to the Iraqi Ministry of Defence.

At least two field commanders of the popular mobilisation forces and a senior federal police officer, who spoke to Al Jazeera on condition of anonymity due to security concerns, said that fighters from Kataib Hezbollah-Iraq, Nujabaa (a faction that split from the Asaib Ahl al-Haq Militia), Jund al-Emam, the al-Battar Brigade and the Ali al-Akbar Brigade, in addition to a brigade of Sunni volunteers, advanced into the centre of Tikrit on Monday. 

Iraqi regular troops were not totally alone there [in Tikrit], but they took the initiative to end the battle and advance into the centre of the city without real ground support provided by the key Shia militias. The tactics, timetables and the high discipline have reflected a new level of performance.

Abdulwahid Touma, independent political analyst

"We broke into Tikrit to the centre and were involved in fierce battles with ISIL fighters who were holed up inside buildings. During the fighting, Kataib Hezbollah joined us and their bravery raised our morale," said one senior field commander of the Sunni brigade in the popular mobilisation forces.

"Badr Brigade [the biggest militia in the popular mobilisation forces], along with smaller militia groups, did not participate in the fighting, but the leaders of all the factions of the popular mobilisation came later and redeployed the troops, and we will move to Beiji town tomorrow," the commander told Al Jazeera. 

Beiji, located 200km north of Baghdad, is home to the biggest oil refinery in the country. While the refinery and the centre of town were taken by the Iraqi army backed by popular mobilisation forces last November, the surrounding villages and towns remain under ISIL control. Beiji is likely to be a stop for Iraqi troops to regroup before resuming the offensive to kick ISIL out from other towns closer to Mosul.  

Tikrit is the capital of Salahudeen province, and ISIL converted its governmental buildings and 13 presidential palaces built by Saddam Hussein, into headquarters for its leaders.

Federal police officers said the battle of Tikrit was complicated by booby traps, roadside bombs, suicide bombers and snipers, which were deployed across Tikrit and slowed the Iraqi troops' advance.

"We would have been able to reach the centre of Tikrit weeks ago, but everything is booby-trapped and we were afraid that we will lose our men if we let them move without the appropriate plans," Brigadier Mohammed al-Baidhani, the spokesperson of the Iraqi Federal Police, told Al Jazeera.

"It is guerrilla fighting, and [the anti-ISIL fighters] have to move from one house to another - so we were advancing very slowly," Baidhani explained.

Political analysts and observers said that Iraqi security forces belied expectations that they would be unable to defeat ISIL without the support of the popular mobilisation forces and their sophisticated weapons.

"Iraqi regular troops were not totally alone there [in Tikrit], but they took the initiative to end the battle and advance into the centre of the city without real ground support provided by the key Shia militias," Abdulwahid Touma, an independent political analyst, told Al Jazeera. "The tactics, timetables and the high discipline have reflected a new level of performance."

Touma added that the experience these troops have gained from fighting alongside the well-trained Shia militias has helped to improve their skills.

"[The Iraqi security forces] have shown that they are able to battle inside the cities without help - which means they are ready to play a bigger role in the coming battles and can be relied upon."

Source: Al Jazeera