MEXICO CITY, July 19 (Reuters) - Mexican President Andres Manuel Lopez Obrador"s inner circle, politicians from every party, dissidents and journalists were potential targets for surveillance by a government client of the Israeli spyware company NSO Group, The Guardian reported on Monday. At least 50 people close to Lopez Obrador were potentially targeted between 2016 and 2017 ahead of his election in 2018, including his wife, children and siblings, The Guardian said. The Guardian"s reporting is based on what the newspaper and others have said was a leak of more than 50,000 phone numbers it said were selected for possible surveillance by NSO Group"s government clients around the world. The list, first accessed by the French nonprofit journalist outlet Forbidden Stories and advocacy group Amnesty International, was shared with The Guardian and more than a dozen other news outlets. Reuters could not independently confirm the existence of the data leak or its contents. NSO Group rejected the reports of a data leak. "This is not a list related to NSO Group, and NSO does not have any target lists. The "list" is derived from services such as HLR Lookup, which is open and free to anyone online," NSO Group said in a statement. "NSO Group will continue to investigate all credible claims of misuse and take appropriate action based on the results of these investigations." Mexico"s defense ministry and attorney general"s office were clients of NSO Group under the previous administration of President Enrique Peña Nieto, according to The Guardian. Those entities did not immediately return requests for comment from Reuters. Peña Nieto"s former spokesman could not immediately be reached for comment. A spokesman for Lopez Obrador, known as AMLO, did not immediately respond to a Reuters request for comment. In 2017, Citizen Lab, a group of researchers based at the University of Toronto"s Munk School of Global Affairs, revealed that civilians in Mexico had been targeted by the software known as Pegasus, which NSO Group only sells to governments. The targets included the phones of journalists, human rights activists and experts backed by the Inter-American Commission on Human Rights who investigated the 2014 disappearance of 43 Mexican students, one of Mexico"s worst atrocities. "The systematic and widespread use of Enrique Peña Nieto"s government to spy on journalists, activists, victims of violence and political opponents is very serious," said Leopoldo Maldonado, director of press freedom group Article 19 for Mexico and Central America. "Spying on President AMLO"s close circle shows this systematic abuse," he said.