WASHINGTON: Police in helicopters and on horseback guarded the US capital on Wednesday as vast crowds were due to come out and party on Independence Day, with security tightened after bomb alerts in Britain.

“We pretty much have all hands on deck,” said Robert Lachance, spokesman for the United States Park Police, the force in charge of security for the festivities.

“We have everybody working and we also employ more than 20 other local agencies to assist us with law enforcement,” he said.

Washington is on code yellow alert — for a “significant risk of terrorist attack,” according to the agency, and the city's security plan drawn up after the attacks on September 11, 2001 was fine-tuned in light of bomb attempts in Britain in recent days.

“That was definitely factored into our plan,” Lachance said. “Whenever something like that happens we always take it into account. We look at our plan to see if we need to change anything.” He predicted the National Mall, a vast open space in the heart of the capital city, would be filled Wednesday evening as crowds of visitors assemble for a firework display, but declined to estimate the number of people expected.

Extra parking restrictions were in force and personnel were instructed to look out for suspicious vehicles, like the explosive gas-laden cars used in attempted atrocities in London and Glasgow, according to reports. Extra security measures were also reported in cites such as New York and Los Angeles.

The fireworks cap a day of parades, floats and marching bands commemorating the United States' declaration of independence from Britain in 1776.—AFP