Graham Arnold suggested Australia could have a "new golden generation" on their hands after they qualified for the last 16 of the World Cup.

The Socceroos' 1-0 win over Denmark on Wednesday meant they finished second in Group D behind France, despite the defending champions losing 1-0 to Tunisia.

Mathew Leckie's goal on the hour-mark was enough for Australia, and head coach Arnold was beaming with pride at his post-match press conference.

"I'm just so proud of the players," he said. "The work ethic, their commitment, their fight, the way they played.

"Denmark are a very good team, they're top 10 in the world for a reason - defensively, I thought we were outstanding."

After their victory against Tunisia, Australia's win meant they achieved consecutive victories at a World Cup for the first time, while they progressed from the group stages for just the second time in six tournament appearances (also 2006).

Thousands of fans gathered at Federation Square in Melbourne to watch the game and celebrate the win, and Arnold believes it shows the impact of football in the country.

"I truly believe the Socceroos are a team that unites the nation," he added. "When the Cricket World Cup is on you don't see Federation Square like that.

"I'm so proud we've been able to put smiles on people's faces. Maybe we should be talking about a new golden generation now, after the golden generation of 2006 who got four points [at the World Cup in Germany], we got six."

Goalscorer Leckie admitted he had "no idea" that Tunisia had scored against France moments before he did against Denmark, meaning Australia had briefly been on course to head out themselves. 

Speaking to reporters, the 31-year-old described his thinking for the goal, saying: "We won the ball, I had one more man to beat, I wanted to cut inside but the defender went that way too, so just in the moment I went left again and swung the left boot.

"For the celebration I didn't really know what to do. I got slapped in the head [by team-mates and substitutes] about 100 times. It shows how much of a team we are. Everyone's here for each other, it's so nice to be a part of this team."

Denmark coach Kasper Hjulmand did not want to speak too much about his team's performance, preferring to wait until he had a chance to process it, but did admit: "We did not reach our level, no doubt.

"We did not produce the quality we can. It is my responsibility that when you come to the World Cup that you reach your best level and we didn't do that."

The Danes had 68.8 per cent possession and created 13 chances, but hit the target just three times at Al Janoub Stadium as they crashed out of the tournament.

"We haven't played with the tempo and rhythm," Hjulmand added. "We started well, but our structures went out of the match. There was too little quality.

"We shouldn't have gone in with such emotion, but should have shown more quality. Our quality was good against France, but in the two other games it was not good enough."

Australia made sure of their place in the third stage of Asia's 2022 World Cup qualifying format with a routine 3-0 victory over 10-man Nepal.

After resounding wins over hosts Kuwait and Chinese Taipai, boss Graham Arnold again rung the changes at Jaber Al-Ahmad International Stadium but it made little difference to the outcome.

Mathew Leckie, captain for the night, gave the Socceroos an early advantage and Fran Karacic's maiden international goal had doubled the lead by the time Rohit Chand was sent off for a professional foul on Martin Boyle before half-time.

Boyle completed the scoring, with a seventh consecutive win to wrap up top spot in Group B long beyond doubt before then.

It took Leckie only six minutes to find the breakthrough, meeting left-back Aziz Behich's cross with a powerful header.

Karacic enjoyed a moment to savour in the 38th minute after Leckie skipped past a desperate lunge from Suman Aryal and picked out the Brescia right-back to slot home.

Leckie was involved again shortly afterwards as Nepal's evening took another sour turn, releasing Boyle to be unceremoniously brought down by Chand, who gave the referee little option.

Boyle looked set to experience personal disappointment when he botched a free header early in the second half before slicing into the side netting. But a sublime curling cross from Hibernian team-mate Jackson Irvine in the 57th minute allowed the 28-year-old to tap in from close range.