Police fired tear gas at the demonstrators who attempted to force their way through a road block on the European side of the city to approach "NATO valley" -the complex of hotels and conference centres where the summit is being held on Monday.
Several police and protesters were reported injured.
Demonstrators, wearing helmets, gas masks and armed with slings, threw petrol bombs, stones and sticks at the police.
Police attempted to break up the demonstration, using armored vehicles and spraying water at the protesters.
The protester overturned at least six cars in the neighbourhood, breaking their windows.
A police officer was seen kicking and hitting a demonstrator with a truncheon.
About 1,500 officers, in riot gear with plastic shields, were deployed in the area as helicopters over flew the district. The leaders at the summit include US President George Bush, British Prime Minister Tony Blair and French President Jacques Chirac.
Turkey dramatically boosted security before Bush's arrival and in preparation for the NATO summit.
Ankara deployed extra security
for world leaders
F-16 warplanes patrolled the skies of Istanbul. AWACS early warning planes dispatched by NATO will help monitor a no-fly zone over the city.
More than 23,000 police are on duty for the summit. Turkish commandos are patrolling the Bosporus in rubber boats with mounted machine guns.
There have been daily protests against the summit and Bush's visit.
Middle East support
On Sunday, more than 40,000 demonstrators, some chanting "USA get out of the Middle East!" gathered on the Asian side of Istanbul, some 10 km away from the summit area.
Police also detained about 15 leftist demonstrators in downtown Ankara, saying the group was planning to stage a firebombing in the city.
Bush's arrival was also preceded by a series of bomb blasts, including one on Thursday that injured three people outside the Ankara hotel where Bush is expected to stay.
Another blast that same day on an Istanbul bus killed four people and injured 14.
The bombings has been blamed on leftists.