Pope Francis has offered his condolences in a phone call to the family of a American journalist killed by Islamic State militants in Syria. Vatican spokesman Fr Federico Lombardi said the Pope phoned relatives of the late James Foley to console them for their loss and assure them of his prayers. The call to the Foley family in Rochester, New Hampshire, came in the afternoon New Hampshire time. Fr Lombardi released no additional details. According to the Associated Press, US officials confirmed the authenticity of a graphic video that showed Islamic State fighters beheading Foley, a 1996 graduate of Marquette University who had been a freelance journalist for the past several years, mostly in the world's trouble spots. In 2011, he was kidnapped on a Libyan battlefield and held captive in Tripoli for 45 days. Sometime in late 2012 he went missing in Syria. The last time his family heard from him was before Thanksgiving that year. The Islamic State militants said they killed Foley in retaliation for US airstrikes on their strongholds, and the group threatened to kill another US hostage also shown in the video. President Obama called Foley's parents, John and Diane Foley, before addressing the nation about their son's death and told them: "We are all heartbroken." When the president was making his televised remarks about James Foley's death, his parents spoke to reporters on the front yard of their home. "We thank God for the gift of Jim. We are so, so proud of him," said Diane Foley. She added that he was "a courageous, fearless journalist - the best of America." John Foley told reporters: "We think his strength came from God", and his wife interjected: "We know it did." His father also described how their son not only wanted to humanise the wars he was covering but would also "take a bullet" for any of his colleagues. "It's not difficult to find solace," his father added, saying he knows his son is "in God's hands". He said it is now up to others to "pick up the gauntlet" and continue the work his son was doing.