Australia hammered Tajikistan 7-0 in AFC World Cup qualifying in Ange Postecoglou's biggest win as head coach.

The Socceroos went ahead through Massimo Luongo in the second minute, then Mile Jedinak slotted home a penalty in the 13th and went into the break at 2-0.

However, the floodgates opened in the second half as another penalty from Mark Milligan made it 3-0 in the 57th minute and Nathan Burns and Tomas Rogic both netted braces in the latter stages to put a gloss on the scoreline.

Greek-born Apostolos Giannou made an instant impact and Australia will advance from the top of their group after a fine night at Adelaide Oval.

Giannou, who described his recent decision to opt for Australia over Greece as the hardest of this life, had four assists on debut and laid off a pass for Luongo's scorching second-minute strike which set the tone of a lopsided fixture.

The striker then earned two penalties before Burns added another when given gold-plated service from Aaron Mooy, who toyed with the Tajiks in a masterful midfield display before 35,439 spectators.

Rogic then came on and scored twice in a three-minute span with sweet strikes -- though one of them denied Giannou a goal. Rogic's 70th-minute blast just cleared the line before rebounding to Giannou, who belatedly tapped in.

Giannou later hit the bar from close range -- one of four Australians to strike the woodwork -- before Burns put the icing on the Socceroos' cake with a headed goal in the 87th minute.

Australia recorded a whopping 38 shots to one from the Tajiks and will keep top of the group ahead of Tuesday night's result against Jordan in Sydney -- the last of the initial stage of qualifying.

With at least a draw, Australia will be assured of advancing to the next round, joining 11 other Asian nations. The draw will be held in April for a stage starting in September.

Information from the AAP was used in this report.