Pau Gasol scored 20 points to lead Spain to a 82-70 victory over Australia, while Russia got 16 points from Andrei Kirilenko in a 73-54 win over China.
Russia and Spain are 2-0 in Group B.
Brazil beat Britain 67-62 in an unexpectedly close game, getting 21 points from Tiago Splitter, another NBA player with San Antonio.
In Group A, Lithuania cruised to a 72-53 victory over Olympic newcomer Nigeria.
Rudy Fernandez added 17 points for Spain, silver medallists at the Beijing Games after losing in the final to the United States.
The Spaniards have several NBA players on their roster, including Gasol (Los Angeles Lakers), his brother Marc (Memphis Grizzlies) and Serge Ibaka (Oklahoma City Thunder).
"We got off to a slow start but we picked it up in the second and in the third we were able to break it open and open a big lead," Pau Gasol said. "Against better teams, we'll have to start better, but we are a team that likes to build, we play better as the tournament gets longer."
Some expect Spain to challenge the United States for the gold again — and that includes Australia coach Brett Brown, an American.
"They have a legitimate chance of knocking the United States," he said.
Marc Gasol added 12 points for Spain (2-0). Australia fell to 0-2.
Kirilenko, who signed a two-year, $20 million deal with the Minnesota Timberwolves last week, also had nine rebounds as Russia easily took care of China, handing it its second defeat in Group B. The former Utah Jazz standout is averaging 25.5 points in Russia's first two games.
"It's tough to play early (9 a.m.) but at least you got a lot of time to rest until the next game," Kirilenko said. "We were physical but so are other teams here."
Russia went on a 10-0 run to open a 20-10 lead and was never really challenged the rest of the game.
Guard Alexey Shved, who is also heading to the Timberwolves, finished with 14 points for Russia and centre Sasha Kaun added 13.
But for Russia coach David Blatt, Shved's performance wasn't good enough.
"Don't get me wrong, I love the kid. But I didn't like the way he played today. Not as well as he could have and should have. He held the ball too long and I'm going to tell him that," Blatt said.
Yi Jianlian, a forward with the Washington Wizards, had 16 points and seven rebounds and was the only China (0-2) player to score in double figures.
Russia pounded China on the boards and finished with a 46-29 rebounding advantage.
Victor Khryapa had 12 rebounds to go with seven points.
Darius Songaila, a former NBA player with several teams, scored 12 points and Linas Kleiza, who plays for Toronto Raptors, had 11 to lead Lithuania past Nigeria.
Rimantas Kaukenas finished with 10 points for Lithuania, which bounced back from an opening loss to Argentina. Nigeria fell to 1-1 after opening the tournament with a win over Tunisia.
Al-Farouq Aminu of the New Orleans Hornets and Ike Diogu had double-doubles for Nigeria. Aminu had 12 points and 11 rebounds; Diogu finished with 12 points and 10 rebounds.
Britain came close to winning its first Olympic game since 1948 but Splitter hit a key layup off a pinpoint pass in traffic from Marcelinho Huertas to make it 65-59.
Luol Deng was then fouled on a three-point attempt, but made only one of his free throws. Britain did not foul and Brazil ran 20 seconds off the clock before Deng fouled Huertas — who sank two free throws with 11 seconds left to seal the game.
Brazil is 1-1 and Britain fell to 0-2.