BAGHDAD — Security measures have been increased at Balad Air Base in Iraq, which houses U.S. Air Force trainers and associated U.S. contractors, following a mortar attack last week, a top Iraqi air force commander said Saturday.

The U.S. military said operations at the base were going on as usual and there are currently no plans to evacuate personnel.

The stepped-up Iraqi security measures at Balad, about 50 miles north of the capital, Baghdad, come amid sharply rising tensions in the Middle East between the United States and Iran. Militants fired three mortar shells into the air base early on June 15, but there were no casualties.

Reuters reported Saturday that Iraqi and and U.S. military spokesmen denied that U.S. forces were preparing to evacuate hundreds of staff of Lockheed Martin Corp. and Sallyport Global from Iraq’s largest air base.

Four separate military sources told Reuters Friday that contractors from the two firms had been preparing to leave Balad over “potential security threats,” the news agency reported.

The new security measures appear to be aimed at alleviating security concerns at the air base, home to a squadron of Iraqi F-16 fighter jets.

Gen. Falah Fares told The Associated Press by telephone that the measures include a night-time curfew, boosting security inside and near the base, as well as surveillance of nearby areas. He said these measures are being carried out in coordination with the U.S.

“All unnecessary movements have been reduced,” Fares said, adding that the curfew now lasts from sunset until sunrise. The curfew had previously been from midnight to sunrise, he said.

Col. Kevin Walker, U.S. Air Forces Central Command director of force protection, denied reports that U.S. forces are evacuating contractors or any other personnel from Balad air base.

"Operations at Balad Air Base are continuing as normal. Claims that personnel are being evacuated are categorically false," Walker said. "There are no plans at this time to evacuate any personnel from Balad."

"The safety and security of all Air Force personnel and those that provide services to the U.S. Air Force are constantly evaluated, and should there be increased threats to our people, the U.S. Air Force will put measures in place to provide the protections required," he said.

Like neighboring Iran, Iraq is a Shiite-majority country, and has been trying to maintain a fine line between allies Tehran and Washington. There have been concerns that Baghdad could once again get caught in the middle, just as it is on the path to recovery.

Iraq hosts more than 5,000 U.S. troops, and is home to powerful Iranian-backed militias, some of whom want those U.S. forces to leave.