New York police arrested a follower of late Muslim cleric Anwar al-Awlaki on suspicion of building a pipe bomb he planned to use against U.S. soldiers returning from Iraq and Afghanistan, officials said on Sunday.

Jose Pimentel, 27, was charged with three terrorism-related counts and two other counts, court documents said.

A U.S. citizen born in the Dominican Republic, Pimentel was arrested on Saturday in a Manhattan apartment while putting the bomb together, police said. They called him a lone wolf who had converted to Islam and became a radical.

In an interview with New York police, Pimentel admitted he took active steps to build the bomb, including shaving the match heads and drilling holes in the pipes and was one hour away from completing it, said the criminal complaint filed by the Manhattan District Attorney.

Pimentel, who has not been charged federally, faces life in prison if convicted.

He was under surveillance since May 2009 and considered New York police cars, a New Jersey police station and U.S. post office among his potential targets, officials said.

As a reader of the online magazine Inspire published by al Qaeda in the Arabian Peninsula, Pimentel took instructions from an article How to Build a Bomb in the Kitchen of Your Mom, Police Commissioner Ray Kelly told a news conference.

We think an event that really set him off was the elimination of Anwar al-Awlaki, Kelly said. His actions became a lot more intense after September 30.

A U.S. drone strike killed Awlaki, a U.S. citizen, in Yemen in late September, ending a two-year hunt. U.S. intelligence called him the chief of external operations for al Qaeda's Yemen branch and a Internet-savvy propagandist.

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

The criminal complaint said a police informant recorded meetings with Pimentel over a period of months and accompanied him as he bought materials for the bomb, including a drill and a clock.

The information from the police could not be independently confirmed.

WE HAD TO ACT QUICKLY

Since the September 11 attacks by al Qaeda in 2001, New York City has considered itself a prime target and has developed extensive intelligence and counterterrorism divisions that employ 1,000 officers within the police department.

No suspects have yet been convicted under New York state anti-terrorism laws, which were passed shortly after the attacks 10 years ago.

New Yorkers have grown accustomed to heightened security and regular announcements that authorities have foiled plots to attack the city. Mayor Michael Bloomberg called the Pimentel case the 14th plot against the city in the last decade.

Most planned attacks - such as the September 2009 arrest of Najibullah Zazi, an Afghan-born man and permanent U.S. resident who plotted a suicide bomb attack on the New York subway system - have been deemed aspirational. Zazi later pleaded guilty.

But some, such as the failed May 2010 attempt to set off a bomb in Times Square, were closer to being carried out.

In that case, a Pakistani-born U.S. citizen, Faisal Shahzad, drove a sport utility vehicle packed with a crude bomb into the heart of Times Square on a busy Saturday evening. The bomb failed to go off and was discovered by a nearby vendor.

Shahzad was later arrested and pleaded guilty.

Kelly said federal prosecutors and the FBI were kept informed of the Pimentel case and that New York police arrested the suspect once he allegedly started to build a bomb.

We had to act quickly because he was in fact putting this bomb together, Kelly said.

Counterterrorism officials in the United States and Europe say lone wolf militants are of particular concern because they can become radicalized via the Internet and prepare for an attack without leaving traces that might draw attention. (Additional reporting by JoAnne Allen in Washington; Editing by John O'Callaghan)