Houston, Jul 17 (IANS): Court martial proceedings began Monday at a US air force base in Texas of a trainer accused of sexually assaulting 10 female trainees, media reported.

Staff Sgt. Luis Walker is among 12 trainers investigated in the widening sex scandal at Lackland Air Force Base in San Antonio, one of the country's busiest military training centres, Xinhua reported citing CBS news.

Military officials say the initial flirtations Walker directed at the women he trained at the base grew into something more sinister: threats and intimidation that eventually led to rape, according to the reports.

Walker, who is the first to stand trial in the sex scandal, faces the most serious charges -- 28 counts of charges including rape, aggravated sexual contact and aggravated sexual assault.

If convicted, he could get up to life in prison and a dishonourable discharge.

The alleged crimes occurred between October 2010 and June 2011, according to an Air Force statement released Monday.

The 10 female trainees Walker is accused of either sexually assaulting or engaging in inappropriate sexual conduct with are expected to testify during the court-martial.

A seven-member jury made up of military personnel will decide the case.

Six of the 12 instructors under investigation face charges ranging from rape to adultery. Officials say nine of those instructors were in the same squadron, according to news report.

At least 31 female trainees have been identified as victims in the overall scandal.