Mufid Elfgeeh, 30, of Rochester, is seen in an undated handout picture released by the Monroe County Sheriff's Office, in Rochester, New York Reuters

A US court has charged a Yemeni-born man for attempting to provide support to Islamist terror group Isis (now known as Islamic State) by recruiting members and plotting to attack US soldiers.

Mufid A Elfgeeh, 30, was arrested in May after attempting to recruit three people for IS, two who were working for the FBI as informants.

"Elfgeeh attempted to assist all three individuals in traveling to Syria to join and fight on behalf of Isis," the Department of Justice said.

He was placed under close surveillance over a year ago following tweets that supported IS, calling on people to donate a portion of their salaries to the Islamist militants.

"As this case shows, our agents and prosecutors are using all the investigative tools at our disposal to break up these plots before individuals can put their plans into action," said Attorney General Eric Holder in a statement.

"We are focused on breaking up these activities on the front end, before supporters of ISIL [another name for Isis and IS] can make good on plans to travel to the region or recruit sympathisers to this cause," he added.

US prosecutors revealed Elfgeeh bought two weapons to carry out shootings, potentially targeting Shia Muslims living in the Rochester area of New York and military personnel returning from the Middle East.

"As part of the plan to kill soldiers, Elfgeeh purchased two handguns equipped with firearm silencers and ammunition from a confidential source," the prosecutors said.

The guns were bought from the FBI informants who had rendered the weapons inoperative before handing them to Elfgeeh.