Hopes of finding the remains of a missing Vatican teenager in the tombs of two 19th-century German princesses have been dashed.

The Vatican has for the first time opened its own investigation into the case of Emanuela Orlandi, a 15-year-old Vatican citizen who disappeared in the summer of 1983.

Pope Francis has declined to accept the resignation of French Cardinal Philippe Barbarin as archbishop of Lyon after he was convicted of failing to report a known predator priest to police, the Vatican said.

Pope Francis has said fear of migration is "making us crazy" as he began a trip to Central America amid a standoff over President Donald Trump's promised wall at the US-Mexico border and a new caravan of migrants heading north.