Moscow, May 26 (IANS): The Russian air force on Tuesday mobilised more than 100 aircraft from their bases to operational airfields as part of a surprise combat readiness inspection, according to the Russian defence ministry.

"The flight personnel have received their flight tasks and started navigational calculations," a statement by the ministry stated, adding that the air units would manoeuvre in the Central Military District reinforced with units from other regions of the country.

According to the defence ministry, the main focus of the inspection is the deployment of field aviation control centers, and rail transport of air defence units to the new positions, Efe news agency reported.

The current exercise -- including some 12,000 troops and as many as 250 helicopters, planes, cargo units -- is in preparation for the Tsentr-2015 military drill scheduled for September.

Meanwhile, the US-led Arctic Challenge Military Exercise (ACE) began on Monday in northern Sweden with participation from nine countries, including six NATO members.

The exercises in the Scandinavian country, which simulates a collective response with the participation of 115 aircraft, including 90 fighter jets and more than 3,500 troops, are considered among the most important in Europe this year.