Security measures have been increased at the Balad air base, one of the country’s largest bases housing American trainers, a top Iraqi air force commander said Saturday. The new stepped-up measures come following an attack that took place last week without inflicting casualties. Gen. Falah Fares told the Associated Press on Saturday that the measures include a night-time curfew, boosting security inside and near the base as well as surveillance of nearby areas. These measures are being carried out in coordination with the US, Fares added. Meanwhile, US forces are preparing to evacuate nearly 400 of staff working for Lockheed Martin Corp and Sallyport Global from the Balad military base where they work as contractors, according to three Iraqi military sources. The evacuation comes over "potential security threats", the sources said without giving details about the threats. Their departure was imminent, the sources noted, Reuters reported. The US military informed Iraqi officials that they would begin evacuating about half of the 800 employees who work for both companies, said a military official with knowledge of the base’s daily operations. The official said the evacuation would take about 10 days.