In this May 18, 2017 photo, anti-government protesters shield themselves from tear gas canisters as security forces disperse an opposition march and block them from reaching the Interior Ministry in Caracas, Venezuela. Venezuela reached almost two months of anti-government unrest in which more than 40 people have been killed. (AP Photo/Ariana Cubillos)

Anti-government protesters face off with security forces blocking an opposition march from reaching the Interior Ministry in Caracas, Venezuela, May 18, 2017. The protest in Caracas comes after a tumultuous 24 hours of looting and protests in the western state of Tachira that led the government to send in troop reinforcements, and after almost two months of unrest nationwide in which more than 40 people have been killed. (AP Photo/Ariana Cubillos)

A water canon sprays government protesters trying to reach the Interior Ministry, in Caracas, Venezuela, May 18, 2017. The protest in Caracas comes after a tumultuous 24 hours of looting and protests in the western state of Tachira that led the government to send in troop reinforcements, and after almost two months of unrest nationwide in which more than 40 people have been killed. (AP Photo/Fernando Llano)

Anti-government protesters make their way to the Interior Ministry, before clashing with National Guards who blocked them in Caracas, Venezuela, Thursday, May 18, 2017. The protest in Caracas comes after a tumultuous 24 hours of looting and protests in the western state of Tachira that led the government to send in troop reinforcements, and after almost two months of unrest nationwide in which more than 40 people have been killed. (AP Photo/Ariana Cubillos)

An anti-government protester is taken away on a motorcycle by other demonstrators after injuring his leg during clashes with security forces in Caracas, Venezuela, May 18, 2017. The protest in Caracas comes after a tumultuous 24 hours of looting and protests in the western state of Tachira that led the government to send in troop reinforcements, and after almost two months of unrest nationwide in which more than 40 people have been killed. (AP Photo/Ariana Cubillos)

A petrol bomb thrown by an anti-government protester burns on the rooftop of a security forces' armored vehicle, in Caracas, Venezuela, May 18, 2017. The protest in Caracas comes after a tumultuous 24 hours of looting and protests in the western state of Tachira that led the government to send in troop reinforcements. More than 40 people have been killed in almost two months of unrest in Venezuela. (AP Photo/Fernando Llano)

Anti-government protesters are met with tear gas fired by security forces as they try to march to the Interior Ministry, in Caracas, Venezuela, May 18, 2017. The protest in Caracas comes after a tumultuous 24 hours of looting and protests in the western state of Tachira that led the government to send in troop reinforcements. More than 40 people have been killed in almost two months of unrest in Venezuela. (AP Photo/Fernando Llano)

Demonstrators hold candles during a vigil for the victims of the clashes with the government's security forces, during protest against President Nicolas Maduro in Caracas, Venezuela, May 17, 2017. Several humanitarian organizations and the opposition have accused the security forces of using too much violence during demonstrations against the government, which have left dozens dead. (AP Photo/Ariana Cubillos)