Media playback is unsupported on your device Media caption New Jersey Governor Chris Christie: "I am responsible for what happened"

New Jersey Governor Chris Christie has fired an aide who allegedly orchestrated traffic mayhem to pursue a political vendetta.

Mr Christie, seen as a potential Republican presidential candidate, apologised over the case, which he said had "embarrassed and humiliated" him.

The gridlock was allegedly engineered to punish a Democratic mayor who did not endorse the governor's re-election.

Mr Christie denied any involvement, blaming "deceitful" staff.

"I'm embarrassed and humiliated by the conduct of some of the people on my team," he said during a two-hour news conference on Thursday in the city of Trenton.

'Abject stupidity'

He said repeatedly that he had nothing to do with the alleged unnecessary closures of traffic lanes, as he announced he had fired his top aide, Bridget Anne Kelly.

Media playback is unsupported on your device Media caption Fort Lee Mayor Mark Sokolich welcomes Chris Christie's apology

"I had no knowledge or involvement in this issue, in its planning or execution," he said, "and I am stunned by the abject stupidity that was shown here."

He spoke as New Jersey's top state prosecutor opened an inquiry into the matter.

On 9 September, two traffic lanes to the George Washington Bridge, which connects New Jersey to Manhattan, were shut for several days.

Emails and texts made public on Wednesday appear to link Ms Kelly to the move.

It caused traffic chaos in the New Jersey borough of Fort Lee, whose Democratic mayor had declined to back Mr Christie in last autumn's gubernatorial election.

"Time for some traffic problems in Fort Lee," Ms Kelly wrote on 13 August to David Wildstein, a political appointee to the Port Authority of New York and New Jersey, which controls the bridge.

Media playback is unsupported on your device Media caption Christie appointee David Wildstein refused to testify in a hearing on Thursday about the bridge scandal

"Got it," Mr Wildstein, who has since resigned, replied.

He invoked his constitutional right not to incriminate himself, pleading the Fifth Amendment, as he testified under oath on Thursday before a state legislature committee that is investigating the scandal.

'Heartbroken'

The governor and Port Authority officials initially said the decision to close the lanes was part of a traffic study.

Chris Christie's career Native of New Jersey, graduated from a law school in the state

First held elective office as a county legislator

Appointed US attorney general for New Jersey by President George W Bush

Ran for and won governor's seat in 2009 against unpopular Democratic Governor Jon Corzine

Some Republicans tried to recruit him to run for president in 2012 but Mr Christie declined

Re-elected by a landslide in 2013 Profile: Governor Chris Christie

"I am heartbroken that someone who I permitted to be in that circle of trust for the last five years betrayed my trust," Mr Christie said on Thursday of Ms Kelly.

He also said he had withdrawn support for his former campaign manager, Bill Stepien, to become New Jersey Republican party chairman, because of the "callous indifference" he had shown in emails about the traffic jams.

The governor also denied suggestions that he had used political intimidation in the run-up to his overwhelming re-election victory in November.

"I am not a bully," he said.

Later on Thursday, Mr Christie travelled to Fort Lee to apologise in person to Mayor Mark Sokolich.

Following the meeting, Mr Sokolich described Mr Christie as "gracious and apologetic".

"I take him for his word," the Fort Lee mayor told US media. But, he added, "we're concerned there is more stuff and more issues to deal with" regarding the incident.

Image copyright Reuters Image caption Bridget Anne Kelly, fired deputy chief of staff of New Jersey Governor Chris Christie

The governor has enjoyed immense popularity in his home state, particularly after his response to Superstorm Sandy, when he praised President Barack Obama's response to the storm and the flooding it caused.

Now commentators are wondering if the bridge scandal will tarnish his White House prospects.

The scandal has blown up as Mr Christie is poised to launch a nationwide travel schedule in his other role as chairman of the Republican Governors Association.