Three action-packed games featured on day seven with South American nation Uruguay progressing to the round of 16, alongside Russia who lead Group A.
Spain and Portugal, who played out a 3-3 draw in an instant classic last week, each notched up their first wins of the tournament.
It comes as the Socceroos prepare to take on Denmark in their second group match on Thursday.
Uruguay 1 - 0 Saudi Arabia
Luis Suarez marked his 100th international cap by sending Uruguay into the last 16 of the World Cup as the striker benefited from some poor goalkeeping to eliminate Saudi Arabia with a 1-0 win.
Suarez tapped in midway through the first half after keeper Mohammed Al-Owais failed to grab the ball on a corner. The goal put Uruguay second in Group A with a maximum six points behind hosts Russia who progressed earlier.
Saudi Arabia, who have not won a World Cup game since their debut in 1994, have zero points, just like Egypt, who lost 3-1 to Russia on Tuesday.
Depending on the result of their last group game against Russia, Uruguay will take on either Spain, Portugal or Iran, who are still on course in Group B for a place in the quarter-finals.
Suarez's goal was by no means pretty, but it did the trick.
At least Suarez, who missed three sitters in Uruguay's 1-0 opening win against Egypt, was his vintage efficient self with his 52nd international goal although he will not have dismissed fears he was not 100 percent fit.
Portugal 1 - 0 Morocco
Cristiano Ronaldo powered-home a fourth-minute header to give Portugal a 1-0 World Cup victory over Morocco that took them top of Group B and meant the unlucky North African side become the first to be eliminated from the tournament.
Ronaldo's fourth goal of Russia 2018, following his hat-trick in the 3-3 draw with Spain, took the European champions to four points. Iran have three points and Spain one ahead of their meeting later on Wednesday.
Morocco, who had a real go at the Luzhniki Stadium but failed to convert their chances, are pointless having also lost 1-0 to Iran and cannot progress to the second round.
Despite their battling display, Morocco will rue the unforgivable defending that made all their subsequent good work irrelevant.
They qualified for the finals without conceding a goal in six matches yet somehow opted against marking the most dangerous attacker at the tournament in the six yard box when Joao Moutinho swung in a cross from a short corner and Ronaldo duly buried the header.
It was his 85th international goal, taking him beyond Hungarian Ferenc Puskas's European record, with only Iran's Ali Daei ahead of him on 109.
Morocco, in their first finals appearance for 20 years, regrouped well and showed some real positivity in attack with Hakim Ziyech and Nordin Amrabat seeing plenty of the ball but Portugal generally defended well to limit the danger.
Amrabat was furious at not being awarded a penalty after wrestling with Raphael Guerreiro and the entire squad erupted in outrage.
Ronaldo heads Portugal 1-0 ahead against Morocco at halftime Source: Reuters
Coach Herve Renard was also ticked off for the new offence of gesticulating to demand a video assistant referee (VAR) review of the incident, which left Amrabat with rugby-style stud-rake marks on his stomach that he insisted on displaying to anyone who would look.
Morocco were the dominant side in the second half and Portugal were grateful to goalkeeper Rui Patricio for a fantastic diving low save to touch clear Younes Belhanda's sharp header, while Medhi Benatia blazed over the bar when he should have scored after an hour.
However, Portugal held out and go on to complete their first-round against Iran while Morocco face Spain, both on June 25.
Spain 1 - 0 Iran
Spain squeezed past dogged Iran in their World Cup Group B encounter thanks to a fortuitous goal from Diego Costa, but the Europeans suffered a string of second-half scares.
The veteran forward notched his third goal in two games when Ramin Rezaeian's attempted clearance bounced off the Spaniard's leg and into the net in the 54th minute.
Though Spain had besieged the Iranian goal in the first half, they were on the back foot for parts of the second, with Karim Ansarifard rifling into the side netting, and Saeid Ezatolahi having a goal ruled out for offside by the Video Assistant Referee (VAR) system.
The result left Spain joint top of their group with Portugal on four points, but Iran close behind on three going into the third and final set of games. After two defeats, Morocco are out
Sergio Ramos of Spain controls the ball under pressure from Sardar Azmoun of Iran Source: Getty
What to expect on day eight
Australia v Denmark 10pm AEST
Peru v France 1am AEST Friday
Argentina v Croatia 4am AEST Friday
Socceroos coach Bert van Marwijk isn't ruling out changes to face a World Cup opponent he rates as a better team unit than France.
Van Marwijk maintains any of the 23 players in his Australian squad are a chance of starting against Denmark in Samara on Thursday.
If the Socceroos lose, they will exit Russia after the group stage regardless of the outcome of their final game against Peru next Tuesday.
Win or draw, and they'll remain a chance of advancing.
Van Marwijk is tunnel-visioned on the challenge presented by a Danish team ranked No.12 in the world.
And he says the Danes are better team than world No.7 France, who pipped Australia 2-1 in the tournament opener.
"The Danish, they are a strong team," van Marwijk told reporters.
