Defending champion Germany beat South Korea 1-0 to move into second position in their group, behind medal hopeful the Netherlands.
And Mink van der Weerden scored twice as the Dutch team beat Belgium 3-1 for its second win of the tournament to go top of Group B.
Despite the two wins, the Dutch are not yet happy with their form in London.
"We have to fix the little things, the little things that go wrong," he said. "I have not got a real reason. Sometimes we have to trap the ball twice, or the pass goes just behind, but we'll be all right."
Britain took an early lead against South Africa in their Group A match through Ashley Jackson's corner. South Africa looked to have stolen the win with two goals inside five minutes late in the second half by Austin Smith and Jonathan Robinson, but Jackson secured a draw by scoring his second with less than three minutes left to play.
Britain almost snatched a win but South Africa goalkeeper Erasmus Pieterse saved a last minute penalty corner.
"It was very exciting," Pieterse said. "I saved the penalty corner with my left arm. It hit me right there."
Five different players got on the score sheet for Australia, which took a 3-0 lead into half time and then put two more past Spain after the break, including a last minute corner by Eddie Ockenden.
"We're fully aware of how good all the other teams are and how good we need to play to win," said Australian defender Liam de Young. "I don't think we have achieved perfection, but we strive to achieve it."
Australia has now scored 11 goals without conceding in its two wins on the blue artificial turf of the Riverside Arena and sits atop Group A.
Pakistan registered its first win of the London Games by beating Argentina 2-0, thanks to penalty corners either side of halftime.
"We just needed three points," said Pakistan defender Rehan Butt. "It doesn't matter if it's with a two goal difference or one goal.
"Next game we are playing Great Britain. I think for Pakistan and for Great Britain we have the same feelings because there's a do or die match for the second place."
Argentina defender Pedro Ibarra, who scored for his team against Britain Monday, was doubtful of his teams' ability to progress to the tournament's next stage.
"We had control of the game but we didn't make use of our chances, especially in the penalty corners. We are going to have to work really hard, but I think it means we won't qualify for the semifinals," he said. "I am fed up."
New Zealand handed India its second straight defeat, rallying from a goal down to win 3-1.
A 33rd-minute goal by forward Christopher Zeller gave Germany the victory over South Korea in the last match of the day to give the German side hopes of progressing to the semifinals.