Three Kenyan-born Americans have been arrested by the FBI for allegedly supporting ISIS.

According to NBC News, officials said Muse Abdikadir Muse, 23, his brother Mohamud Abdikadir Muse, 20, and another relative, 26-year-old Mohamed Salat Haji, are naturalised US citizens who were born in Kenya.

They have been charged with conspiring to provide material support to a terrorist organisation.

FBI agents arrested Muse Muse at Gerald R. Ford Airport in Grand Rapids on Monday, when he was about to take a series of flights that would have eventually landed him in Mogadishu, Somalia, according to a federal complaint. Mohamud Muse and Haji were arrested hours later.

The three defendants had all “pledged allegiance to ISIS through videos they recorded themselves,” according to a statement by the Department of Justice quoted by NBC News.

Haji and Mohamud Muse had “aided in the purchase of the ticket and drove Muse Muse to the Grand Rapids airport, each knowing the true purpose of the travel was for Muse Muse to join and fight for ISIS,” federal authorities said.

The news outlet said all three men face up to 20 years in prison if convicted.

“Muse Muse and Haji allegedly discussed with each other their desire to join ISIS, to kill non-believers, and even to potentially use a car for a martyrdom operation to run down non-believers here in the United States if they could not travel overseas to fight for ISIS,” according to prosecutors.

It wasn’t immediately clear if the three men had lawyers.

The investigation began in April 2016 when agents found pro-ISIS writings on Mohamud Muse’s Facebook page and they were later contacted by an FBI agent, posing as an ISIS recruiter, according to the federal complaint.

Muse Muse’s airfare was $1,799 and the family asked for the phony ISIS recruiter to contribute $1,200, officials said. The FBI said it came through with the $1,200, to help buy the ticket