Islamic State militants have stepped up their attacks on security forces in north-eastern Iraq, reportedly killing at least 18 people since the weekend. Four tribal militia fighters and three soldiers died in three incidents in Salahuddin, Kirkuk and Diyala provinces on Monday night, security sources said. Diyala also saw multiple attacks and clashes on Saturday and Sunday. Analysts believe IS is taking advantage of the coronavirus pandemic, which is occupying the authorities' attention. Politicians are also distracted by talks on the formation of a new government and the impact on the economy of the collapse in global oil prices. At its height in 2014, IS controlled some 88,000sq km (34,000sq miles) of land stretching from western Syria to eastern Iraq, and imposed its brutal rule on almost eight million people., Iraqi pro-government forces declared victory against the jihadist group in late 2017, but several thousand militants are believed to be still active in the country. Many have been hiding out in and mounting attacks from tunnel networks and caves in the Hamrin mountains, which straddle Diyala, Kirkuk and Salahuddin. In one of Monday night's attacks, militants opened fire at an Iraqi army checkpoint on the boundary between Kirkuk and Salahuddin, about 160km (100 miles) north of the capital Baghdad, killing the two soldiers, a security source in Kirkuk said. Another attack left four members of the paramilitary Tribal Mobilisation Force dead in the village of al-Asiriya, near the town of Tuz Khurmatu, the source added. A third soldier was killed in the Abu Khamis area, 25km (15 miles) north-east of Baghdad, according to a security source in the city of Baquba. On Sunday, five Tribal Mobilisation Force fighters were killed in clashes with IS militants in the village of Umm al-Karami, in north-western Diyala, while a soldier was shot dead by a sniper in the Ain Laila area, security sources said. Four police officers reportedly died on Saturday in an attack in the town of Zaghnia, north of Baquba, while a bomb killed a solider in al-Uzaim. IS cells have also been hiding out in the remote Western Desert of Anbar province, where Tribal Mobilisation Force units launched an operation on Monday. A military source said three militants were killed in the Mud ham area, two of whom blew themselves up when surrounded inside a mosque.