The suspect, who was identified as Leeland Eisenberg, 47 years-old, walked into the street-level office at about 1 pm, told people to lie on the floor and demanded to talk to Clinton.

He claimed he had a bomb strapped to his chest with duct tape. After five hours of tense negotiations by cell phone and after he released all the hostages, Eisenberg walked out of the office with his hands in the air. A SWAT team surrounded him with guns drawn and Eisenberg  was handcuffed, placed in a tactical response vehicle and driven to the Rochester Police Department.

The purported bomb strapped around the man's chest proved to be a bundle of road flares with "no ability for it to detonate," town police chief David Dubois said.

Clinton, a US senator for New York who leads the race for the centre-left Democratic Party's 2008 presidential nomination, voiced relief that her young campaign workers emerged physically unscathed.

"I am very grateful that this difficult day has ended so well," the wife of former president Bill Clinton said outside her home in Washington. "All of my campaign staff and volunteers are safe."

"I want to thank them for their extraordinary courage and coolness under some very difficult pressures," she said in televised remarks.

Clinton expressed her gratitude to the team that resolved the hostage situation. "I want to thank them for their professionalism and their extraordinary work today," she said. "We're immensely relieved that this has ended peacefully."

Leeland Eisenberg, who has a history of a mental illness, initially took four adult hostages but immediately released a woman with a small child, police said.

"A young woman with a 6-month- or 8-month-old infant came running into the store just in tears," Lettie Tzizik, an employee of nearby Carney Medical Supply, told WMUR-TV. "You need to call 911. A man has just walked into the Clinton office, opened his coat and showed us a bomb strapped to his chest with duct tape."

But he kept other kept three young Clinton campaign workers - two women and a man. Other woman managed to escape around 3 pm.

CNN reported that Mr Eisenberg called its newsroom several times throughout the afternoon and talked to staffers. According to CNN, Mr Eisenberg said he had mental problems and couldn't get anyone to help him.

Clinton was hundreds of miles away in the Washington area, but she cancelled an appearance at a party meeting outside the capital after news of the hostage drama.

In downtown Rochester, nearby campaign offices for rival Democratic candidates Barack Obama and John Edwards closed after the hostage-taking.

According to Rochester Police Chief David Dubois Eisenberg faces multiple charges, including criminal threatening, kidnapping and reckless operation and he could face additional federal charges.