The Iraqi government has received a delivery of Russian-made fighter planes it hopes will turn the tide against ISIS rebels who have seized large parts of the country.Iraqi security officials confirmed five Sukhoi jets, which were purchased second-hand from Russia, had arrived in Baghdad on Saturday.Pictures released by the defence ministry show the jets taxiing on a runway towards a hangar.The planes are expected to bolster efforts by the Iraqi armed forces to retake territory seized by rebels led by self-claimed the Islamic State in Iraq and al Sham (ISIS) earlier in June.The Iraqi government launched its biggest push yet to drive back the rebel offensive on Saturday, as soldiers backed by tanks and helicopter gunships began an offensive to retake the northern city of Tikrit.There were conflicting reports as to just how much headway the Iraqi military made in its initial thrust towards Tikrit, the hometown of Saddam Hussein, according to the AP news agency.The Tikrit operation, if successful, could help restore a degree of faith in the security forces, as well as embattled Prime Minister Nouri al-Maliki.