(CNN) -- An indictment unsealed in New York Tuesday provides further evidence of links between al Qaeda affiliates in Somalia and Yemen, a growing concern to counter-terrorism officials.
And the indictment also sheds light on the Obama administration's policy on how to handle terror suspects detained overseas.
The indictment charges Ahmed Abdulkadir Warsame with providing material support to the extremist group Al-Shabaab in Somalia, and to al Qaeda in the Arabian Peninsula (AQAP) in Yemen. He is also charged with conspiring to teach and demonstrate the making of explosives.
If convicted, he faces a mandatory life sentence.
Warsame, a Somali national, was captured by U.S. forces on April 19 in what the U.S. attorney's office in New York describes only as "the Gulf region." He was interrogated overseas for "intelligence purposes" for two months before finally being transferred to FBI custody and brought to the United States Tuesday, when he made an appearance in federal court.
During that appearance, he pleaded not guilty, according to Ellen Davis, spokeswoman for the U.S. attorney's office. Warsame was held on a U.S. Navy ship in the Gulf region after his capture until being brought to New York for Tuesday's court appearance, according to the attorney's office.
Neither the indictment nor the accompanying press release disclosed where the interrogation took place, but there is a substantial U.S. naval presence in the Arabian Sea.
According to the indictment, Warsame, said to be in his mid-20s, provided material support for Al-Shabaab, which controls large areas of central and southern Somalia. He also provided the group with explosives, weapons and communications equipment.
He also spent time in Yemen in 2010 and earlier this year, allegedly receiving explosives and other training from al Qaeda in the Arabian Peninsula, which in the past two years has emerged as one of the most active parts of the organization.
Unconfirmed local reports in Somalia have spoken of Al-Shabaab boats leaving Kismayo for southern Yemen as Islamist groups there -- including al Qaeda - have taken advantage of a growing political vacuum.
Warsame is also alleged to have tried to broker a weapons deal with AQAP on behalf of al Shabaab. Both groups are designated as terrorist organizations by the United States.
U.S. officials have recently spoken of growing links between Al-Shabaab and AQAP, and their ambitions to hit targets overseas. A joint Pentagon-CIA task force has recently stepped up pressure on Al-Shabaab, visiting Somalia to gather intelligence against the group.
Late last month a U.S. drone strike against an al-Shabaab camp near the southern port of Kismayo is said to have killed several militants.
CNN's Susan Candiotti contributed to this report.