The Defence Force says a third soldier has been formally charged in relation to civilian deaths in Afghanistan.

In September, the Director of Military Prosecutions said she intended to charge three soldiers over the deaths last year.

Two soldiers were charged at the time, but the third soldier could not be formally charged because he was travelling overseas.

The Defence Force says the soldier has returned to Australia and has been served with the charges.

It says all three soldiers are being provided with the best possible support during the legal process.

Six people, including four children and a suspected Taliban insurgent, were killed when the Australian commandos attacked a compound in Uruzgan province in February 2009.

It is believed the men have been charged with various service offences, including manslaughter, dangerous conduct, failing to comply with a lawful general order and prejudicial conduct.

Earlier this year, the two soldiers initially charged strenuously denied the allegations.