Authorities insist they will not allow this year's summit of the Group of Eight industrialized nations to be riven by protests, such as last year's chaotic array of blockades and window-breaking in Scotland or the violence in Genoa, Italy, in 2001 in which one demonstrator died.

Activists hope leaders of the other seven countries attending the G-8 summit, which opens on Saturday, will press President Vladimir Putin to better respect human rights. Putin has come under criticism - in particular from the United States - about democratic backsliding during his more than six years in power.

Vladimir Soloveichik, one of the protest organizers, said that by Friday morning, some 200 activists had been detained on their way to St. Petersburg from around the country, while 30 more had been detained in the city itself.

City police said people were detained on a daily basis for offenses such as violating rules on officially registering their presence in the city, and that there was no way of determining which among them might be anti-globalization protesters. They did not say how many people had been detained.

Protest organizers vowed to hold a march on Saturday despite authorities' refusal to grant permission - necessary under Russian law for any demonstration to be held.

"We will try a march tomorrow under any circumstances, a peaceful march," said Ilya Ponomaryov, one of the protest organizers.

Activists have been angered by the extremely tight leash Russian authorities have put on them. The only authorized site for protests this year is a deteriorating stadium at the hardest-to-reach tip of one of the city's islands.

Not only is it far from the summit site, some 20 kilometers (12 miles), it is remote from everything else, too. The nearest public transit stop is a three-kilometer (two-mile) hike through a park - and even that stop was shut down for the duration of the summit.

About 300 people were at the stadium on Friday for the protest, which is going by the carefully non-inflammatory name of "The Russian Social Forum." Organizers last week said they were expecting about 2,000 people to attend.

St. Petersburg Governor Valentina Matviyenko visited the stadium for about 20 minutes on Friday morning, but insisted no marches would be allowed because "in the circles around anti-globalists, there are unfortunately some radical elements."

City officials have refused permission for a march that would have ended at the Neva River berth of the Aurora, the gunship that fired the shot that was the signal for the storming of the Winter Palace in the 1917 Bolshevik Revolution. They also refused permission for a march by the Communist Party.

Asked why protesters were being kept in a remote part of city, she argued it was no different to where the summit itself was being held - the ornate Konstantin Palace in the suburb of Strelna.

Over the past few days, organizers have claimed that activists have been detained, ejected from trains and planes, assaulted and put in jail on trumped-up charges.

Such actions "cannot be called otherwise than state extremism," Lev Ponomarev, director of the prominent Russian watchdog group For Human Rights, said on Thursday.

Ponomarev said his organization filed a complaint with the Prosecutor-General, asking that criminal abuse of police power be prosecuted.

Police, including the feared OMON riot forces, made a quiet but visible showing at the stadium.

Few activists from outside the former Soviet Union were in evidence at the stadium and they may be under even tighter constraints than the Russians. Foreigners must register in any Russian city within three days and such registration is nearly impossible without fixed accommodation.

Despite the restrictions, some activists may try for direct confrontation. An Internet message board for G-8 protesters is carrying a message that is either a warning or a goading call to action: a photo of a fat man with a pacifier in his mouth and the slogan "The anti-summit isn't child's play - if you're not certain, sit at home."