Mayor of Sicilian town of Palma di Montechiaro, Pasquale Amato, poses in the council hall of Polistena, Calabria, Italy June 24, 2016. Amato has received four letters containing death threats within the space of a month. REUTERS/Tony Gentile

A memorial plaque reporting the names of victims of mafia violence in Polistena, Calabria, Italy June 24, 2016. REUTERS/Tony Gentile

Customs officers examine bags of fertilizer, some of the 30 tonnes seized from a ship from Malaysia, at a customs office in Denpasar, Bali, Indonesia September 22, 2016 in this photo taken by Antara Foto. Antara Foto/Nyoman Budhiana/via REUTERS

A man walks on the rubble of houses at the site of a Saudi-led air strike in the Red Sea port city of Hodeidah, Yemen September 22, 2016. REUTERS/Abduljabbar Zeyad

People gather at the site of a Saudi-led air strike in the Red Sea port city of Hodeidah, Yemen September 22, 2016. REUTERS/Abduljabbar Zeyad

People gather at the site of a Saudi-led air strike in the Red Sea port city of Hodeidah, Yemen September 22, 2016. REUTERS/Abduljabbar Zeyad

People gather at the site of a Saudi-led air strike in the Red Sea port city of Hodeidah, Yemen September 22, 2016. REUTERS/Abduljabbar Zeyad

People gather along the shore of the Mediterranean Sea during a search for victims after a migrant boat capsized, in Al-Beheira, Egypt, September 21, 2016. REUTERS/Stringer