Jose Pimentel, charged on three terrorism-related counts is believed to be a follower of Anwar al-Awlaki [Reuters]

New York authorities have arrested an alleged al-Qaeda sympathizer in a suspected plot to build a pipe bomb to kill government workers and returning US soldiers, officials have said.

Jose Pimentel, a 27-year-old Dominican man who resides in New York and has US citizenship, was charged with three terrorism-related counts, court documents showed on Sunday.

Michael Bloomberg, the city's mayor, announced the arrest and charges at a joint news conference on Sunday evening with the city's police commissioner and district attorney.

Bloomberg said Pimentel had planned to target police, postal facilities and others and said he was a "lone wolf" without affiliation to foreign terrorist organisations.

City Police Commissioner Raymond Kelly said Pimentel, though not affiliated with an outside group, was a follower of slain Islamic cleric Anwar al-Awlaki, who was killed in a US raid in Yemen on September 30.

"He talked about changing his name to Osama Hussein, to celebrate his heroes, Osama bin Laden and Saddam Hussein," Kelly said.

Kelly said Pimentel had followed an online magazine from Awlaki, including an article entitled "How to make a bomb in the kitchen of your mom."

Pimentel "talked about killing US servicemen returning from Iraq and Afghanistan, particularly US army and marine corps personnel," the police chief said.

"He talked about bombing post offices in and around Washington Heights and police cars in New York City, as well as a police station in New Jersey.

"We think what set him off was the elimination of Anwar al-Awlaqi."

While Pimentel's planning had allegedly been in process since before the killing of Awlaki, the commissioner said that "his actions became a lot more intesnse after September 30".

The death of Awlaki, who suspected of involvement in several attacks on the US and of recruiting Americans for his cause, was criticised by some people as an extrajudicial killing by US forces.