Alex Ritson

Sebastian Asha.

Just weeks before a presidential election in Colombia, at least 14 people have been killed in a bomb attack on a bus in the southwest of the country.

The attack is part of the latest wave of violence which has been blamed on dissidents from the now defunct FARC rebel group.

Hugo López is the commander of Colombia's armed forces.

This is a terrorist attack against the civilian population.

It occurred in a district of Cali in Cauca on the Pan-American Highway.

There was a roadblock set up by the terrorists who used a bus and another vehicle to block the road.

Our South American expert for BBC Monitoring, Luis Fajardo, joined us from Miami.

Tell us who these dissident factions are.

Yeah, as you say, elections coming and the security situation is not great.

Today marks 40 years since the worst nuclear disaster in history at Chernobyl in northern Ukraine, which was then part of the Soviet Union.

A reactor explosion released significant radioactive contamination across Europe.

Charles Bremer was Moscow bureau chief for the Reuters news agency at the time and one of the first reporters to get close to Chernobyl after the accident.

He's been speaking to Caroline Wyatt.

We didn't really know how much we had to be afraid.

We knew there was a lot of radioactivity, but there were a lot of wild rumors.

And we didn't know what the truth was because the Russians were telling us absolute lies on one side.

And there was a lot of hysteria in the West, if you remember, or maybe you don't.

A lot of media in the West was saying there were hundreds and thousands of people who were dead there.

It was a big unknown because these were the days before the internet, social media.