"ISIL militants attacked the Aalas Oilfield [in eastern Tikrit], where they clashed with security forces," Ghazwan al-Jabouri, an Iraqi police captain, said on Wednesday.

According to al-Jabouri, a policeman was killed in the attack, which was ultimately thwarted by security forces.

The Iraqi air force repelled a simultaneous attack in northern Tikrit, al-Jabouri added, killing four ISIL militants in the process.

Despite the army’s recent capture of most of Saladin from ISIL (including the Al-Shirqat district which was taken late last month), the extremist group remains active in several parts of the province, from which it continues to stage attacks on security forces.

In recent months, ISIL has stepped up attacks on areas held by the government in conjunction with its declining influence in northern and western Iraq.

Iraq has suffered a devastating security vacuum since mid-2014, when ISIL captured the northern city of Mosul and overran large swathes of territory in the northern and western parts of the country. 

Recent months have seen the army -- backed by a 60-nation air coalition and local allies on the ground -- retake much territory. Nevertheless, the extremist group remains in control of several parts of the country, including Mosul.

The Iraqi army and its allies are now gradually advancing on Mosul, which officials in Baghdad have vowed to "liberate" by year’s end.