Killing of Ecuador presidential candidate Fernando Villavicencio investigated by FBI

US FBI agents have joined officials in Ecuador investigating the killing of presidential candidate Fernando Villavicencio.

Arrests have already been made after Villavicencio was shot entering a car after a rally in the country's capital last week.

Over the weekend, a notorious gang leader, Jose Adolfo Macias, known as "Fito", was arrested for allegedly making death threats towards Villavicencio before he was killed.