A member of a police bomb squad patrols the oval in front of the Hatch Shell with a dog ahead of the city's Fourth of July Independence Day celebrations in Boston, Massachusetts July 4, 2013. Security officials said they would deploy record numbers of police and install scores of new surveillance cameras and checkpoints around fireworks displays, concerts and other Fourth of July events in Boston, New York, Washington and Atlanta. [Photo/Agencies]

BOSTON - Less than three months after bombs ripped through the heart of Boston, residents and visitors face heavy security as they celebrate Independence Day at an open-air concert and fireworks display on the banks of the Charles River.

Like the Boston Marathon, where two pressure-cooker bombs killed three and injured more than 260 on April 15, the Boston Pops' July Fourth concert on the Esplanade is one of the city's most cherished events and routinely draws half a million people.

This year, security is tighter than ever, police said, noting that hundreds of additional state and local police plus federal officials will be patrolling the city as well as the area around the Hatch Shell where the orchestra will play.

"We were walking around last night and we saw guys in sniper outfits," said Cindy Munroe, visiting from Coventry, Rhode Island. "It was making me a little nervous, but we're probably safer here than anywhere else right now."

By mid-afternoon, with temperatures reaching a steamy 92 degrees Fahrenheit (33 Celsius), concertgoers were setting up tents and parasols as others sat on lawn chairs and blankets.

To reach the amphitheater where conductor Keith Lockhart will lead the Pops through Tchaikovsky's 1812 Overture and other patriotic favorites, revelers passed through tightly controlled checkpoints, some manned by soldiers in camouflage gear. On the river, marine patrols kept watch from afar and wireless surveillance cameras were set up in trees and on poles.

Security was "obviously all over the place," said Derek Switaj, a student at Boston College, adding, "I feel safe, I feel fine, and I'm excited for tonight."

For days, police have sealed manhole covers and removed trash cans plus anything where bombs could be hidden. Police have also received millions of dollars worth of equipment, including handheld instruments that can detect whether bags hold explosives, from private companies, the firms and police said.

"We are certainly focused on this event and that people get here safely and get out safely," Boston Police Commissioner Ed Davis told reporters as the city put final touches on preparations for its biggest public event since the marathon.

After the bombing, the surviving suspect, Dzhokhar Tsarnaev, told officials that he and his brother, Tamerlan, considered attacking the city on July 4 but moved up the timing after building the bombs more quickly than initially planned, law enforcement sources have said. Tamerlan Tsarnaev died in a shootout with police.

In the last days, police assured Boston and the country that there is no imminent danger. "There are no threats out there toward this particular event," Massachusetts State Police Colonel Timothy Alben told reporters. "But that won't affect the intensity of scrutiny."

Officials, including Massachusetts Governor Deval Patrick, who locked down the city and some suburbs as police searched for the Tsarnaev brothers on April 18 and 19 after they were identified on video cameras, urged the public to enjoy the festivities as usual.

Visitors will have to brave the day's heat with fewer amenities, however. Coolers with wheels are banned as are backpacks, sharp objects, cans, and glass containers, police said. Revelers may bring in only clear liquids in clear bottles and food in clear bags, officials explained.

By late afternoon, a large portion of the grassy oval remained empty. Some visitors sounded a determined note, showing their support for the city and the holiday.

"We don't want to lose our freedom, right?" said Munroe, the visitor from Rhode Island.

Nicole Mierzwa, who is visiting from Rochester, New York, on a 13-week nursing assignment, said she was not put off by what happened in April.

"There are crazy people everywhere, and you just have to carry on and do your thing and not be afraid," she said, standing at the edge of the lawn. "It is a little bit frightening to see machineguns and the SWAT team but it's good that they're prepared and they're taking it seriously."