BEIJING — Giant screens were set up in parks so Beijing residents could share in the glory of their city hosting the lavish Olympics opening ceremony today. But in at least one park, security guards shut the gates and shooed people away.

Main roads were quiet, with police cars stationed at every intersection. In old Beijing neighborhoods, security volunteers in Olympic T-shirts sat on street corners or cycled around looking for any hint of trouble.

After seven years of buildup and billions of dollars in preparations, the capital declared today an unofficial holiday and encouraged millions of residents to stay home or use public transport. Officials said it was an effort to reduce traffic congestion as 91,000 people attended the opening of the Beijing games.

The Olympics have been a huge source of national pride. But they have also come at a cost for the residents of Beijing, a city of 17 million where half the cars have been taken off the roads, and many migrant workers and students have been sent home to reduce pollution and congestion.

As fireworks lit up the smoggy skies above the National Stadium to begin the ceremony, the gates of one park in the north of the capital were promptly locked with only a few hundred people inside. Several dozen residents called on police to open the gates and let them in, but were denied.

"You're not letting ordinary people into the park," shouted one elderly woman carrying a foot stool and grabbing the bars of the gate. She said she was too scared to give her name.

In alleyways near the ancient Lama Temple, people watched televisions in hair salons and restaurants. But outside, the streets were mostly empty except for security volunteers.

Zheng Zhifeng, 29, who runs a tailor shop with his wife near the Lama Temple, said there were no customers as everyone was at home watching the ceremony on TV.

"We didn't think the Olympics would be this grand," he said. "It's very exciting."

Liu Yidong, 53, who works at a hotel, said Chinese are not as outgoing as Westerners, and did not need to celebrate outside.

"Still, everyone thinks it is a very festive occasion," he said.

In the center of the city a few blocks from Tiananmen square, Cui Dajie fanned herself in her fruit shop as thousands gathered to watch the fireworks.

"I don't have time to watch. I have to make money," she said.

Hundreds of enthusiastic Chinese who were not able to get into the Beijing National Stadium for the opening ceremony went to a street about a mile away to enjoy the atmosphere.

Shouting the Beijing Olympic slogan "One World, One Dream" and "Go China, Go China," the crowd waved national flags as they waited for the fireworks.

For Chinese dissidents, human rights lawyers, and other activists who have dared to challenge the communist government, the start of the Olympics meant more surveillance and tighter restrictions.

"I have no plan for tonight," Jiang Tianyong, a human rights lawyer, said from his home. "It's not my Olympic Games. It's not the games for the ordinary people."

Associated Press Writers Chi-Chi Zhang, Cara Anna and Didi Tang contributed to this report.