Gamba claimed top spot in Group E and crucial home advantage in the one-off last 16 encounters after beating China's Tianjin Teda 2-0 on Wednesday to complete a clean sweep for Japan. Kashima Antlers and Nagoya Grampus had already secured passage to the next round before this week's final round of group matches.

With Al Hilal, Al Shabab and Al Nassr also making it through on match-day six, Saudi Arabia also have four representatives in the next phase after two-time champions Al Ittihad were the first to secure their place in the knockout stage earlier this month.

And in another intriguing tie, Group C winners Al Ittihad will entertain Saudi champions Al Hilal, while Al Shabab travel to Qatar to face Al Sadd and Al Nassr face a daunting trip to Iran to face last year's runners-up Zobahan.

Sepahan and Bunyodkor complete the last 16 line-up in the West with the Uzbekistan champions traveling to Iran, with all eight ties to be played on either Tuesday May 24 or Wednesday May 25 ahead of September's quarterfinals, which will be played over two legs.

In the East, China's sole representative Tianjin Teda must travel to Korea to face 2006 champions Jeonbuk Hyundai Motors after conceding top spot in Group E to Gamba.

K-League champions FC Seoul claimed first place in Group F after sharing a 1-1 draw in China with Hangzhou Greentown on Wednesday to set-up a last 16 meeting with Japan's Kashima.

Japanese champions Nagoya, meanwhile, will travel to Korea to face Group H winners Suwon Samsung Bluewings after losing 3-1 at Al Ain on Wednesday to open the door for FC Seoul.

With Tianjin already sure of qualification for the first time from Group E but with top spot still up for grabs, a free kick from Japan international Yasuhito Endo opened the scoring for Gamba before substitute Takashi Usami's stoppage-time penalty settled the contest at Expo '70 Stadium.

"I am feeling relieved as we got through this stage," said Gamba manager Akira Nishino. "It was a game we played with a lot of extra pressure.

"It's a pity that we now have to play against a Japanese side but we focused on nothing but winning the group. I will think about how to play them a little later."  In Group G, tournament debutants Cerezo thumped Shandong Luneng 4-0 on Tuesday to qualify for the second round at the expense of the Chinese Super League champions.

Needing just to avoid defeat to advance as runners-up and finish behind Jeonbuk, Rodrigo Pimpao set the home side on their way after 39 minutes before Hiroshi Kiyotake, Takashi Inui and substitute midfielder Shu Kurata sealed the win after the break.

Jeonbuk recorded a fifth win in six games as a hat trick from Krunoslav Lovrek inspired a 6-0 win over Arema Indonesia at Jeonju World Cup Stadium as the 2006 champions comfortably secured top spot and home advantage against Tianjin.

Inaugural AFC Champions League winners Al Ain of the UAE signed off their campaign with a 3-1 win over Nagoya, which ended the visitors' hopes of topping Group F.

With a stoppage-time header from youngster Zeng Yue earning Hangzhou a 1-1 draw with FC Seoul, Nagoya knew a win in the Middle East would secure top spot but the visitors were 2-0 down at the break as Hamad Al Merri and Elias struck for already-eliminated Al Ain.

Jungo Fujimoto reduced the margin just after half time, but Al Ain quickly restored the two-goal cushion as Elias scored from the spot to hand Nagoya a trip to Suwon after the K-League side beat Shanghai Shenhua 3-0 on Tuesday.

Ha tae-goon struck twice while Shin Se-gye was also on target at Shanghai Hongkou Stadium as Suwon edged out Kashima on goals scored despite the Japanese side coming from a goal down to beat Sydney FC 2-1 at the National Stadium in Tokyo thanks to goals from Yuya Osako and Takuya Nozawa.

In the West, Al Hilal secured their place in the last 16 from Group A with a comfortable 2-0 victory over Qatar's Al Gharafa at King Fahd International Stadium on Wednesday.

Needing just a point to go through ahead of Al Gharafa, second half goals from Yasser Al Qahtani and Ahmed Al Fraidi sealed the win. But with Sepahan rallying from a goal down to post an emphatic 4-1 victory over Al Jazira of the UAE, the three points was not enough to earn Al Hilal top spot.

Javad Kazemeyan pulled Sepahan level in Abu Dhabi after Brazilian Bare had opened the scoring for Al Jazira before a double from Senegal's Ibrahima Toure completed the turnaround with Reza Enayati sealing victory for the visitors.

Elsewhere, qualifiers Al Sadd sealed top spot in Group B as Madji Siddiq's stoppage-time free kick earned a 1-1 draw at already-eliminated Pakhtakor of Uzbekistan.

And Al Nassr narrowly joined Al Sadd in the last 16 despite suffering a 2-1 defeat to Iran's Esteghlal in front of 85, 422 at the Azadi Stadium in Tehran. Badar Al Motawa had opened the scoring for the visitors on the hour mark, but after Farhad Majidi equalized, Hawar Mulla Mohammed netted with a minute remaining for Esteghlal. But after losing 2-1 in Saudi last month, Esteghlal missed out on goal difference with Al Nassr prevailing by just two goals.

In Group C, Al Ittihad ensured a home tie in the last 16 as Nuno Assis' goal earned a 1-1 draw with Uzbekistan champions Bunyodkor at Prince Abdullah Al Faisal Stadium on Tuesday.

Finally in Group D, Al Shabab beat Zobahan 1-0 on Tuesday to join last year's runners-up in the last 16. Fisal Bin Sultan's neat finish three minutes before the hour mark proved the difference as Al Shabab claimed the points they needed to stay ahead of Emirates, who suffered a 2-0 defeat at Al Rayyan.