An Islamist extremist group known as Jabhat al-Nusra or the Nusra Front released American journalist Peter Theo Curtis earlier on Sunday, the U.S. government and U.N. have confirmed.

The al-Qaida-affiliated group had held Curtis hostage for the past two years, according to ABC News, but the group handed back the American journalist to U.N. peacekeepers at the Golan Heights near Lebanon.

In a statement, the U.N. confirmed the handover: "The United Nations can confirm that it facilitated the handover of Peter Theo Curtis. He was handed over to UN peacekeepers in Al Rafid village, Quneitra, the Golan Heights. ... After receiving a medical check-up, Mr. Curtis was handed over to representatives of his government."

After the news of Curtis's release became public, his mother, Nancy Curtis, released a statement of thanks for the return of her son, according to ABC News.

"My heart is full at the extraordinary, dedicated, incredible people, too many to name individually, who have become my friends and have tirelessly helped us over these many months," she said. "Please know that we will be eternally grateful."

Secretary of State John Kerry also released a statement concerning Curtis's release, saying that Curtis's mother had "simply refused to give up and has worked indefatigably to keep hope alive that this day could be a reality."

"Over these last two years, the United States reached out to more than two dozen countries asking for urgent help from anyone who might have tools, influence, or leverage to help secure Theo's release and the release of any Americans held hostage in Syria," he said.

According to Al-Jazeera, one of the countries that helped was Qatar, which mediated the negotiations for Curtis's release. Earlier in the year, in June 30, the Nusra Front released a video of Curtis speaking about his captivity from a prepared statement. He said, "Everything has been perfect, food, clothing, even friends now."

However, in the wake of the murder of James Foley at the hand of extremist group ISIS, Secretary Kerry said in his statement about captured Americans, "We continue to use every diplomatic, intelligence and military tool at our disposal to find them and bring our fellow citizens home."