NEW YORK (Reuters) - United States authorities have accused a New York City college student of plotting to set off a pressure cooker bomb in the city in support of the militant group Islamic State in Iraq and Syria (ISIS), according to court documents made public on Tuesday.

Munther Omar Saleh, 20, was arrested early on Saturday morning after he and another man got out of their car and ran towards a surveillance vehicle that had been tracking their movements, according to documents filed in federal court in Brooklyn.

A defence lawyer for Saleh could not be identified on Tuesday. The other man, who was also arrested, was not named in the court documents and could not immediately be identified.

A federal agent said in court papers that Saleh, a resident of the New York City borough of Queens, spent hours online researching how to build a pressure cooker bomb and reading accounts of the deadly 2013 Boston Marathon bombing.

In numerous online postings, Saleh expressed support for ISIS and at one point posted on Twitter, in an apparent reference to the militant group Al-Qaeda, "I fear AQ could be getting too moderate", according to court papers.

He also praised various militant attacks, including the January massacre at the headquarters of the magazine Charlie Hebdo in France and murders carried out by ISIS, the authorities said.

A police officer observed Saleh on successive days in March on foot at the George Washington Bridge, which connects New Jersey and New York, seemingly looking around, the court papers said.

The behaviour prompted officers to interview Saleh, who denied sympathising with ISIS and granted them permission to examine his computer, the authorities said. Investigators found the computer contained ISIS propaganda, according to court filings.

Saleh is studying at a college that specializes in aeronautics, the court papers said.

The complaint filed against Saleh mentions a third unnamed co-conspirator but does not say an arrest has been made.

A spokesman for the Brooklyn US Attorney's office, which is prosecuting the case, declined to comment.

US authorities have charged a number of so-called "lone wolf" plotters in recent months who have apparently been inspired by ISIS, and the authorities have said they are pursuing similar cases in all 50 states.