New signing Alessandro Diamanti starred with two magical strikes as AFC Champions League title-holders Guangzhou Evergrande fought back from two goals down to beat Melbourne Victory 4-2 on Wednesday.

In a dream debut, the 30-year-old Italian international inspired a rousing second-half comeback as the Marcello Lippi-coached Chinese champions opened their trophy defence in style at a packed Tianhe stadium.

First-half goals from Pablo Contreras and Leigh Broxham threatened a huge upset in Group G but after the break, Guangzhou scored four goals in 26 minutes through Huang Bowen, Elkeson and Diamanti.

Victory got their opener on 36 minutes, when a Jesse Makarounas free-kick from the left was poorly dealt with, Kosta Barbarouses fired in a shot and Contreras tapped in the rebound.

The goal stunned Guangzhou and their massed ranks of red-clad fans, but there was worse to come just five minutes later-and again from the delivery of Makarounas, also from the left but this time from a corner.

Again the high ball was not cleared and Broxham was perfectly placed to lash home a superbly controlled volley from the edge of the box and give the visitors a shock 2-0 lead at half-time.

However, Lippi's men returned from the break fired up and a dipping Diamanti free-kick drew a diving header off the line from Contreras.

Diamanti had a hand in Guangzhou's first goal when he fed Luo Jiacheng for a cross which was emphatically volleyed into the net by Huang.

And the Italian made it 2-2 when, after timid defensive work from Victory's Adama Traore, he turned and hammered a fierce shot on his favoured left foot past static goalkeeper Nathan Coe.

Brazilian striker Elkeson put the champions 3-2 ahead when he brilliantly controlled a long, high ball from the halfway line on his chest and squirmed a low shot through the legs of Nicholas Ansell.

Victory looked a beaten team but Diamanti made sure of the win when he effortlessly shimmied past Contreras and prodded a pin-point strike inside the far post with the toe of his left boot.

Earlier Australian debutants Western Sydney Wanderers had a harsh welcome to the competition when they threw away an early lead to lose 3-1 at home to 2012 champions Ulsan Hyundai.

The Wanderers scored after just 42 seconds at home through Brendon Santalab, but the South Koreans punished defensive mistakes to score through Kim Shin-Wook, Ko Chang-Hyun and Kang Min-Soo.

Also in Group H, Brazilian midfielder Renato scored from a first-half free-kick as Japan's Kawasaki Frontale kick-started their campaign with a 1-0 home win over Guizhou Renhe of China.

And in Wednesday's other Group G game, 2006 winners Jeonbuk Hyundai Motors scored three times in 10 second-half minutes as they beat Japan's Yokohama F. Marinos 3-0.

Meanwhile in West Asia, a goal from Karim Ansarifard with eight minutes remaining saw 10-man Tractorsazi Tabriz edge two-time champions Al Ittihad of Saudi Arabia.

Despite the dismissal of Ali Karimi in the 60th minute after he collected his second yellow card of the match, Iran's Tractorsazi netted the Group C game's only goal through Ansarifard who produced a fine solo run from inside the Al Ittihad half and slotted the ball into the bottom right-hand corner of the post.

Former Qatar champions Lekhwiya however crashed to a 2-1 defeat against Al Ain with Diaky Ibrahim and Asamoah Gyan finding the target on either side of the break. Vladimir Weiss scored the only goal for Lekhwiya in the Group C match.

In Group D, 2011 champions Al Sadd dominated Iran's Sepahan for a 3-1 victory in Doha.

Former Asian Player of the Year Khalfan Ibrahim put the hosts ahead in the 18th minute but Mehdi Sharifi equalised for Sepahan in the 78th.

However, a Nadir Belhadj strike off an Ibrahim pass saw Al Sadd nose ahead in the 83rd minute and Brazilian pro Rodrigo Tabata put the issue beyond doubt for the defending Qatar Stars League champions with an injury-time effort.