GUATEMALA CITY, July 24 (Reuters) - Hundreds of Guatemalans protested outside the presidential palace on Saturday against the ouster of anti-graft fighter Juan Francisco Sandoval, who fled the country overnight after being stripped of his post in a move that sparked a global outcry. Sandoval, who had led the Guatemalan Special Prosecutor"s Office Against Impunity (FECI) until Friday, fled to the Salvadoran border in the wee hours of Saturday, according to the country"s human rights ombudsman Jordan Rodas. "The decision was made to safeguard his life," Rodas told Reuters. Guatemala"s Attorney General Maria Porras removed Sandoval from his post on Friday as the head of FECI, which was originally created to tackle investigations spearheaded by the U.N.-backed International Commission Against Impunity in Guatemala (CICIG) but was ousted from the country in 2019. In a press conference hours before his departure, Sandoval said he would challenge his "illegal dismissal." He accused the attorney general of asking his agency to seek her opinion on any case that involved the government. "I am the latest in a string of prosecutors who have suffered the consequences for seeking truth and justice," he said. In April, the Guatemalan Congress refused to appoint another high-profile anti-corruption crusader, Magistrate Gloria Porras, to the nation"s highest court. The Guatemalan government said in a statement on Saturday that it "categorically rejects Juan Francisco Sandoval"s statements." Sandoval"s dismissal underscores the challenges U.S. President Joe Biden"s government faces in pursuing its anti-graft push in Central America, where it says corruption and impunity are drivers of migration. "Guatemala"s AG fired corruption prosecutor Sandoval for being too effective against organized crime and its links to politicians....USG (U.S. government), your move," wrote former U.S. Ambassador to Guatemala, Stephen McFarland, on Twitter. Attorney General Porras held a previously scheduled meeting with representatives of 13 donor countries and organizations on Saturday, her spokesman told Reuters. Sandoval"s dismissal was discussed at the gathering, a source with knowledge of the meeting told Reuters, with Porras saying the effort to combat corruption would continue under new leadership. No other details were immediately available. Guatemala"s most powerful campesino groups have called for a general strike on Monday.