The terror plot that has New York on heightened alert today was reportedly personally orchestrated by Osama bin Laden’s successor as part of an effort to avenge the terror lord’s death.

Ayman al-Zawahiri, bin Laden’s longtime deputy, personally recruited three terrorists to travel to the US to detonate car-bomb attacks to coincide with the tenth anniversary of 9/11, according to The Daily.

The attacks are al-Zawahiri’s pledge to avenge bin Laden’s death, ABC News reported.

Once here, the men “may have met up with a small cell or other suspects,” sources told The Daily.

READ FBI’S TERROR ALERT MEMO (PDF)

COMPLETE 9/11 ANNIVERSARY COVERAGE

PHOTOS: NYPD KEEPING NYC SAFE

All three operatives speak fluent English and two of them believed to be American citizens, the sources said.

Vice President Joe Biden, during an appearance on ABC’s “Good Morning America,” said, “We don’t have the smoking gun, but we do have talk about using a car bomb.”

The details of the plot come amid heightened security following the “credible” threat as police officers swarmed subway stations, bridges and tunnels in a show of force.

Bloomberg, who took the subway to City Hall this morning from his Upper East Side home, said, “We don’t want al Qaeda or any other organization … to take away the freedoms.”

The mayor, who took a downtown No. 5 train to work, added, “I’m going to do what I do every day.”

The Port Authority said it has increased police presence and bag checks at Kennedy, Newark and LaGuardia airports. The agency has also increased vehicle checks at all its bridges and tunnels.

On his radio show this morning, Bloomberg said that police, already on heightened alert for 9/11, have ratcheted up manpower to the max.

“Are we increasing it a little more? Yeah,” the mayor said on his weekly WOR radio show. “But there’s a limit on how much you can have because you can’t have a cop on every corner.”

Without giving specific details of the new threat, Bloomberg said it was being taken seriously because it wasn’t “outlandish.”

“Credible means it’s possible to do. If someone says they’re going to do something so outlandish, they’re never going to get the resources,” he explained. “They couldn’t possibly do it. But something that is possible.”

NYPD spokesman Paul Browne said that 911 calls of reports about suspicious packages and vehicles have risen significantly. But he noted that nothing so far has been found.

This comes after a “specific” and “credible” terror threat against New York and Washington, DC, was revealed Thursday night — involving three men who entered the country last month from Pakistan and were instructed by al Qaeda to detonate a car bomb on the 10th anniversary of 9/11, law-enforcement sources told The Post.

The information, which came from chatter picked up overseas by the CIA, said the attack would occur on the 10th, 11th or 12th, the sources said.

“It does feel more operational than most of the others we’ve had that have been more aspirational,” another source said.

NYPD officials have also been briefed in recent days about three men who were arrested in Ottawa with 2,000 pounds of stolen explosives, as well as two men captured in Berlin.

Cops are checking whether those arrests are connected to the possible anniversary attack, sources said.

“The NYPD, FBI and entire intelligence community have been on heightened alert,” Mayor Bloomberg said at a late night press conference at Police Headquarters.

“We know terrorists view the anniversary as a time to strike again. Over the next few days, we should all keep our eyes wide open.”

Police Commissioner Ray Kelly said cops will work an extra four hours on their shifts through Monday, and promised more vehicle checks on bridges and tunnels — using bomb-sniffing dogs, radiation detectors and automatic license-plate readers.

Kelly also said there would be more bag checks on subways, and increased vigilance on illegally parked cars.

“We have to be concerned. Terrorism is theater and this is a stage, right now probably the world’s biggest stage,” Kelly told CNN.

“We have the opening of the 9/11 memorial, the president and two former presidents here, obviously a lot of high profile public officials will be here, so we have to be concerned.”

In a statement this afternoon, Gov Cuomo said, “The reports of a new possible terrorist threat against New York are cause for renewed vigilance and awareness, but not alarm or panic. We will not allow the terrorists to dampen our spirits on this anniversary.

“Our state and local law enforcement officials are always at the highest state of alert. New Yorkers should feel confident that everything that needs to be done is being done to keep the city secure.”