The Socceroos only had to avoid a five-goal defeat to confirm their appearance at a sixth consecutive finals and goals from Connor Metcalfe and Mitch Duke earned the Australians a come-from-behind win to brush aside the Saudis.

Abdulrahman Al-Obud had given the home side a glimmer of hope when he netted from close range in the 19th minute but Metcalfe equalised with three minutes left in the half to extinguish Saudi dreams.

Duke then put the visitors in front in the 48th minute when he glanced Martin Boyle's free kick past Nawaf Al-Aqidi before Mat Ryan, making his 100th appearance for his country, saved a late penalty save to deny Salem Al-Dawsari an equaliser.

The win confirms the Australians as second-place finisher in Group C behind Japan, who secured their spot at the finals in March.

"It is special. It probably hasn't sunk in yet," said Tony Popovic, who took over as coach last September after Australia made a stuttering start to the third round of qualifying. 

"It's been a very intense period since I've joined. We've built a good foundation now (but) we want to really get better, kick on and try and do something special at the World Cup." 

Saudi Arabia took third place in Group C and will feature in a fourth phase of qualifiers in October alongside Indonesia, Qatar, the United Arab Emirates, Iraq and Oman.

The Omanis kept their hopes alive at the expense of Palestine as Issam Al-Sabhi's penalty deep into stoppage time earned the Gulf side a draw that kept them in fourth place in Group B.

A header by Oday Kharoub gave Palestine a 49th-minute lead and a second yellow card for Oman's Harib Al-Saadi had put Ihab Abu Jazar's side in control until the dying minutes, when Muhsen Al-Ghassani was brought down in the area.

Al-Sabhi stepped up to send goalkeeper Rami Hamada the wrong way to seal fourth place in the group for Oman and eliminate the heartbroken Palestinians.

Earlier in the evening, Japan crushed Indonesia 6-0 with Daichi Kamada scoring twice in the first half in Osaka as the Samurai Blue won Group C while Wang Yudong's late penalty had China finish their campaign with a 1-0 win over Bahrain.

Iran confirmed themselves as Group A winners with a 3-0 win over North Korea that came after Kye Tam was sent off for the visitors with 24 minutes remaining in Tehran.

Mehdi Mohebi, Mehdi Taremi and Amirhossein Hosseinzadeh were all on target in the last 16 minutes to guarantee first place for the Iranians, who had secured their berth in March.

Already-qualified Uzbekistan took second spot with a 3-0 win against Qatar in Tashkent while the United Arab Emirates claimed third ahead of the Qataris despite conceding a late goal to draw 1-1 with Kyrgyzstan in Bishkek.

South Korea completed their commitments in Group B with a 4-0 thrashing of Kuwait to ensure Hong Myung-bo's World Cup-bound outfit topped the standings with an unbeaten record.

Jordan, who qualified for their first World Cup on Thursday, finished second in Group B despite losing 1-0 to Graham Arnold's Iraq in Amman.