The Asian champions advanced to the knockout stage with a perfect record of three wins in Group A but the business end of the tournament promises tougher challenges.

Japan were confident from the start, having secured a top two finish in Group A, after beating Paraguay and USA in their earlier matches.

It was Japan's second successive win and sealed their place in the knockout stage, with the Asian champions having defeated Paraguay 5-4 in their opener on Thursday.

Japan will play Switzerland, who edged Paraguay 7-6 in extra-time, on Monday with the East Asian side only needing a draw to win the group.

Both sides played a patient game and neither was able to break the stalemate in the first period.

That changed 48 seconds into the second period as Masanori Okuyama broke the deadlock in style, before Ozu Moreira doubled Asian champions Japan's lead in the 16th minute.

The 2015 champions, Portugal, were made to sweat, though, as both sides exchanged goals in the first period through Coimbra’s penalty in the fifth minute, before Oman's Jalal Al Sinani equalised with a free header four minutes later.

Be Martins scored the only goal of the second period and it was a beauty. The diminutive and skilful player hit a blistering shot into the top corner from distance, with Oman’s Younis Al Owaisi left helpless in the 21st minute.

UAE needed a win to advance to the knockout stage but Senegal scored three times in the final period to seal a quarter-final meeting with Portugal.

Having lost 8-2 to reigning champions Brazil on Friday, Oman needed to win against Nigeria and did it in thrilling fashion.

They face Portugal on Tuesday where another three points will take them to the knockout stage.