An American journalist held hostage in Syria by a militant group linked to al-Qaida was released on Sunday.

The release of Peter Theo Curtis, 45, had been facilitated by the Gulf emirate of Qatar. It came just days after the barbaric execution of American reporter James Foley by Islamic militants.

According to US Secretary of State John Kerry, Theo Curtis was kidnapped and held hostage for nearly since 2012 by Jabhat al-Nusra, also known as the Nusra Front, an al-Qaida-linked militant group fighting the government of Syrian President Bashar Assad.

Qatar's government said on Sunday that the emirate had "exerted relentless efforts to release the American journalist out of Qatar's belief in the principles of humanity and out of concern for the lives of individuals and their right to freedom and dignity.”

It was not immediately clear what prompted Curtis’ release but his relatives said that while they were not privy to the exact terms, they were told that no ransom had been paid.

Curtis’ release came after the jihadist militant group Islamic State (IS) last week released a video purportedly showing the beheading of American journalist James Foley, blaming his death on US airstrikes against their fighters in Iraq.