Tens of thousands of Americans gathered at the National Mall in downtown Washington and its surrounding areas on Sunday night, to watch a display of fireworks marking the nation's 228th Independence Day.

Some highways and roads leading to the National Mall were closed, and traffic controls were enforced in places where people were gathering to watch the fireworks display.

In Charleston, West Virginia, US President George W. Bush marked the day with a stump speech on Iraq and the economy.

"This history we celebrate today is a testament to the power of freedom to lift up a whole nation. And we still believe on America's 228th birthday that freedom has the power to change the world," he told a gathering of hundreds of supporters.

Bush, who was about 90 minutes late arriving there because of mechanical problems with his presidential jet Air Force One, was forced to cancel an appearance at a religious service.

Hailing the US economy as "healthy and growing," Bush said terrorist threats to the United States were "very real."

"We know that terrorists want to strike our nation again," he said.

Police patrols were increased and security was tightened for the holiday.

In a weekly bulletin to state and local law enforcement agencies on Thursday, the Federal Bureau of Investigation (FBI) urged law enforcement officials to increase patrols and watch for possible terror threats timed to the July 4 holiday.

The FBI said that there was no specific, credible threat of a terror attack, but the United States remained a top al Qaeda target, and warned of potential July 4 attacks by al Qaeda members using tactics like assault teams, car bombs and suicide bombs.

US officials have warned since April that al Qaeda might take advantage of holidays or special events over the summer to attack the United States or US interests, but the Homeland Security Department said it had no plans to raise the nation's color-coded terror alert level.

Source: Xinhua