Russia has delivered a batch of fighter jets to the Iraqi government that they hope will help government forces fight to retake northern parts of the country from Islamic militants, Baghdad said Sunday.

Iraqi security officials said the five second-hand Sukhoi jets arrived on Saturday and would be ready for use within days, the BBC reported. Iraq is expecting another shipment in the near future.

Iraq is combating an offensive by Sunni jihadist group the Islamic State of Iraq and the Levant (ISIL) that has overrun swaths of five provinces, killed nearly 1,100 people, displaced hundreds of thousands and threatened to tear the country apart. ISIL has also established control in eastern Syria and is seen as a regional threat.

After several weeks on the defensive, Iraqi troops backed by helicopter gunships launched an operation early Saturday aimed at dislodging ISIL forces from the northern city of Tikrit, one of two major urban centers they seized in recent weeks in a dramatic blitz across the country. The Sunni-majority city was the hometown of former Iraqi leader Saddam Hussein.

Military officials sought to portray the push that began before dawn as a significant step that puts the army back on the offensive. They said the operation includes commandos, tanks and helicopters, as well as pro-government Sunni fighters and Shiite volunteers.

Residents in Tikrit have confirmed fighting, but the extent and effectiveness of the assault were still unclear.

While the attack is reportedly being coordinated with US military advisers, American officials have stressed that US personnel are not involved in the fighting.

On Friday, senior Obama administration officials were quoted saying Jordan may ask Israel and the United States to help it fight ISIL if it threatens Amman.

According to a report by The Daily Beast, the officials told senators in a classified briefing earlier this week that ISIL is eyeing Jordan as well as its war-torn neighbors, and that some of its jihadists have already tweeted out photos and messages saying they have seized a key Jordanian town.

The Daily Beast quoted one of the Senate staff members who attended the briefing as saying that, according to the administration officials, if Jordan were to face a military onslaught from ISIL, it would “ask Israel and the United States for as much help as they can get.”

AFP contributed to this report.