Romania beat neighbours Hungary 3-0 in a World Cup qualifier at the National Arena on Friday to climb to second place in Group D and improve their chances of reaching the playoffs.
Netherlands, who visit Estonia on Friday, top the standings with 18 points from six games, followed by Romania on 13 from seven matches. Hungary are third with 11 points from seven games.
Scuffles had broken out ahead of the qualifier with police reporting seven injuries before the match started.
Police said Hungarian supporters threw bottles, smoke bombs and fire crackers, and caused damage to restaurants and bars in a tourist area of the city. They said five supporters and two police officers were injured.
Medical emergency service spokesman Bogdan Oprita said three Hungarians were hospitalised with head injuries.
Media reported that riot police used tear gas and batons to quell the violence.
There was a heavy police presence in Bucharest with riot police and a line of buses waiting for supporters outside the main railway station.
Some 1,900 police were present for the match. After scuffles at the stadium, police kept supporters apart.
The home side took control with their first attack when Ciprian Marica stole the ball off Richard Guzmics, came face to face with keeper Adam Bogdan and calmly slotted home in the second minute for his third goal in the qualifying campaign.
Romania continued to press forward and Mihai Doru Pintilii doubled their lead with a thunderous 25-metre shot that gave Bogdan no chance after 31 minutes. It was Pintilii's first international goal in 14 appearances.
Bogdan Stancu almost got his name on the scoresheet midway through the second half but embarrassingly missed the target from the edge of the penalty area with only keeper Bogdan to beat.
Hungary came closest when Razvan Rat made a vital interception to deny Daniel Bode and Cristian Tanase made it 3-0 with a class finish with two minutes remaining.
Romania host Turkey on Tuesday in their next qualifier and Hungary take on Estonia.
Uzbekistan came from a goal down to earn a valuable 1-1 draw against Jordan in the first leg of their 2014 World Cup Asian playoff.
Jordan opened the scoring in the 29th minute when Ahmad Hayel exploited some poor Uzbek defending to pick out Mus'ab Allahham in the penalty area, with Allahham's shot giving goalkeeper Murotjon Zukhurov no chance.
Uzbekistan responded with an equaliser just five minutes later with a long shot by captain Server Djeparov.
Tuesday's second leg at Pakhtakor Stadium in Tashkent will decide which team reaches the intercontinental playoff against South America's fifth-place qualifier.
Both teams picked up the pace in the second half at King Abdullah II International Stadium, with Jordan coming closest to scoring with a series of shots in the final minutes.