Five Iraqi army officers were killed on Saturday by a roadside bomb planted on the border between Iraq and Jordan, according to an Iraqi military source.Col. Walid al-Dalaimi, an officer in Iraq's Anbar Operations Command, said an explosive device -- planted close to the Karamah Border Crossing near the village of Trebil -- had destroyed a passing military vehicle, instantly killing the five officers.According to al-Dalaimi, the bodies of those killed -- who included a captain, a first lieutenant and three lieutenants -- were taken to Jordanian capital Amman, from where they will be flown to Baghdad.In a related development on Saturday, Iraqi military sources told Anadolu Agency that the army had stepped up its campaign against the ISIS militant group -- which remains in control of broad swathes of the country -- and had recently killed a number of the group's fighters.In hopes of cutting the group's supply lines between the Falluja and Saladin provinces, Iraqi army forces are now trying to regain control of the buffer zone between the Jazeera Samaraa and Tharthar regions and Ramadi city, Anbar's provincial capital.While ISIS has lost a number of areas that it captured last year in the Diyala, Nineveh and Saladin provinces, it remains in control of most of Anbar.Iraqi forces and allied militias, including Kurdish Peshmerga forces, have continued to try to recover all ISIS-held areas and flush the group's fighters from flashpoint regions.