Sniffer dogs and heightened security greet NFL fans after Paris attacks

From Seattle to New York, the National Football League stepped up security inside and outside of stadiums on Sunday as America's most popular sports league responded to a series of coordinated attacks across Paris that left at least 129 dead.

Football fans, who were subject to vehicle searches and banned from bringing backpacks and purses into arenas, greeted new measures with a mixture of good humour, annoyance and resignation.

“We’ve had our 9/11. They had what happened to them. We're all one, without question. We sympathise absolutely,” said Craig Corcoran of the Bronx, referring to the September 11, 2001, attack on New York’s World Trade Center.

“It's not going to stop us from having a good time. Over there, it's the same way. They're still going to go out and have their fun and they should,” Corcoran said while tailgating in the parking lot outside of MetLife Stadium in East Rutherford, New Jersey.

While the U.S. Department of Homeland Security informed the National Football League there were no known specific threats, Commissioner Roger Goodell was taking no chances and ordered beefed-up security at all venues.

“The safety of our fans, stadium personnel, and teams at all NFL games is our priority, and security at our games is robust,” the league said.

The NFL and other North American professional sport leagues went on high alert after one of the attacks on Friday targeted a friendly soccer match between France and Germany where suicide bombers apparently attempted to enter the Stade de France, in a suburb just north of Paris.

At Baltimore's MT&T Bank Stadium, K-9 units were visible outside the venue and inside around the concourse for the Ravens' game against the Jacksonville Jaguars, ESPN reported.