The Macedonians earned a sixth successive win with a 68-59 defeat of Slovenia, while Finland rekindled their hopes of reaching the quarter-finals with an 87-73 win over eliminated Georgia.
Russia and Macedonia, who had earlier booked their berths in the last eight, head the group with a 4-0 record and Greece are also assured of a spot in the knockout stage with two wins and two defeats in the second group stage.
Finland, playing in their first major tournament since Eurobasket 1995, will advance to the knockout stage for the first time if they win their dogfight against Slovenia on Monday, with both teams on a 1-3 record.
Having arrived in neighbouring Lithuania as one of the dark horses of the 24-team event, the Russians cruised through their preliminary pool and kept improving as they overpowered one rival after another.
"We are playing better and better every game and this was our best game in the tournament so far," said Russia's Utah Jazz forward Andrei Kirilenko, who helped the team to their first title as an independent nation in 2007.
"We showed a lot of power in offense today and we were also good defensively, so we now have high hopes of emulating our 2007 success, although we will be up against a strong team in the quarter-finals no matter what.
"Any of the six teams in the other group can be champions on their day but hopefully we can go up into the medal rounds," added Kirilenko, who scored 13 points to go with eight rebounds against the Greeks.
Centre Timofey Mozgov led the winners with 19 points and forward Aleksey Shved added 15 as Russia had 13 team rebounds and eight assists more than the Greeks.
Finland had never made it past the preliminary round. Having reached the second stage in Lithuania, they are now one win away from their biggest success after squeezing into Eurobasket 2011 through a late qualifying play-off.
A balanced team effort against the Georgians, in which six players ended in double scoring digits, was a perfect birthday present to their point guard Teemu Rannikko and veteran power forward Hanno Mottola.
"It was a nice birthday gift from the team for me and Mottola ... We knew we could compete here but we also knew we would have to play at a very high level," said Rannikko.
"We have a big game on Monday and we have to do the same things we have been doing so far, which is to move the ball well in offense and make open perimeter shots.
"Slovenia are a very good team with a lot of established Euroleague players, so it's going to be difficult."
Mikko Koivisto led the charge with 14 points for Finland, who landed a staggering 13 three-pointers from 26 attempts against only four of 19 converted by Georgia, having also grabbed 17 offensive rebounds.
Macedonia, playing in only their third major tournament as an independent nation, continued to defy the odds as they beat yet another more heralded team.
American-born point guard Lester Bo McCalebb, the driving force behind Macedonia's success, shone again with a game-high 19 points against the Slovenians, whose point guard Goran Dragic was a lone beacon of light with 20 points.
Vlado Ilievski added 14 points for the Macedonians and Vojdan Stojanovski chipped in 11 to send their colourful and vociferous band of supporters into raptures in the 11,000-capacity Siemens Arena.
On Sunday, Serbia play Turkey, unbeaten France clash with holders Spain, and hosts Lithuania take on Germany in a fiercely competitive Group E, with all six teams still vying for the other four quarter-final berths.
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