A woman poses for a picture between the Roman numerals for the NFL Super Bowl XLVIII football game in Hoboken, New Jersey, January 29, 2014. [Photo/Agencies]

Bomb attacks of the kind that tore through mass transit sites in Russia ahead of the upcoming Sochi Olympics are a top concern of security officials preparing for Sunday's Super Bowl, the head of the New Jersey State Police said on Wednesday.

While law enforcement officials said they were not aware of any specific threats targeting the Feb. 2 NFL championship in East Rutherford, New Jersey, they regard attacks of the kind that killed 34 people in two days in Russia late last year as their greatest concern.

"Of particular concern to us is what was going on overseas in Volgograd in regard to the Sochi Olympics, as you know both of those bombings were targeting mass transit," Rick Fuentes, superintendent of the New Jersey State Police, told reporters. "That is a concern with the mass transit, we've prepared ourselves for it."

New York Police Department Commissioner William Bratton added that while officials were focused on that type of attack, they were not aware of any specific plans to target the game or surrounding events.

"We are keeping an eye on activities around the world, but certainly at this time there are no threats directed at this event that we're aware of," Bratton said.

The stadium is located about 10 miles (16 km) west of New York City, site of the Sept. 11, 2001, attacks. It has been locked down for a week and authorities are scanning all vehicles that go in, a practice that will continue on game day, officials said.

About 400,000 people are estimated to have traveled into the region for events surrounding the game, though only about 80,000 fans will get to MetLife Stadium on Sunday.

Thousands of security officers will be on hand for the Sunday game, and fans will be prohibited from bringing bags into the stadium unless they are clear and no larger than 12 inches by 6 inches by 12 inches (30 cm by 15 cm by 30 cm), with women's purses limited to 4.5 inches by 6.5 inches (11.4 cm by 16.5 cm).

Throngs of uniformed police have been stationed around Super Bowl-related events throughout the region, from the street fair set up along New York's Broadway, where normal trash cans have been removed and replaced with clear plastic bags that can be easily visually inspected, to Tuesday's media day at a Newark, New Jersey, arena, where fans strained to get a close-up look at the players.

Standing by a black armored police vehicle, 38-year-old Seattle Seahawks fan Eli Montague, of Vancouver, British Columbia, said he thought the security was ample.

"It looks like they have everything under control," Montague said. "I feel safe."