The Taliban has tweeted a photo of a man it says is the Afghan sergeant who gunned down three Australians in a 'green on blue' attack last month.

Australian soldiers Lance Corporal Stjepan Milosevic, Sapper James Martin, and Private Robert Poate, died when an Afghan National Army (ANA) sergeant shot them at close range with an automatic weapon at a patrol base in the Baluchi Valley in Uruzgan province.

The alleged shooter - Sergeant Hikmatullah - escaped over a security fence. Three other Australians were wounded.

The Taliban has now posted a photo of a man it says is Hikmatullah on Twitter.

He is pictured in front of a microphone with an apparent Taliban symbol on it.

The Taliban says he killed six Australians and wounded four others.

The Taliban is known to exaggerate reports of Western casualties.

Seven Australians have now been killed in the so-called green-on-blue attacks, while 12 have been wounded.

Over the weekend six coalition soldiers - two British and four American - were killed in insider attacks, taking the death toll for the year to date to more than 50.

The British soldiers were shot dead by a man wearing an Afghan police uniform as they were returning to base after a patrol.

The Americans were found dead at a remote outpost alongside a dead policeman. Other policemen who were stationed at the observation post have disappeared and are believed to have carried out the attack.

At least 51 foreign military personnel have been killed in "insider" attacks this year, deaths that have badly strained the coalition's relations with Afghan forces as it moves towards handing security responsibility to them by the end of 2014.

ABC/wires