Do you know the Countries which could push the nuclear 'red' button??. :-BBC

The first ever atomic bomb was dropped 70 years ago, as an act of war, killing about 70,000 people in Hiroshima, Japan.

Earlier, Japanese Prime minister Shinzo Abe led a memorial there.

The bombing in 1945 by a US war plane, and a second one on Nagasaki three days later, is credited with ending World War Two.

There have been no repeat acts since then, but we look at countries which have nuclear bombs to use, if needed.

Hiroshima marks 70 years since atomic bomb

There are five permanent members of the UN security council, (the body established after World War Two of the world's leading nations) which officially have nuclear weapons.The countries who have nuclear weapons

These countries are the UK, Russia, US, China and France.

Image captionOne of the UK's Trident nuclear submarines based at HMS Vengeance at Faslane

In the UK, the current military nuclear weapon system, Trident, is often criticised as being too expensive to maintain and unnecessary in its mission to keep world peace by some politicians and political parties.

A map of the UN security council members who have nuclear capability

Image captionThe UN security council members who have nuclear capability

But the Conservative government believes having Trident gives the UK a place at the top table in the international community and is seen as the ultimate war deterrent.

There are also four nuclear countries that aren't recognised as Nuclear Weapons States.

India conducted a successful test in 1974, although they have a "no first use" policy and will only act in retaliation.

Due to the tension between the two countries, when India got close to making a nuclear weapon Pakistan began its own project.

As the only Muslim country with nuclear capabilities some people have called Pakistan's nuclear capability "the Islamic bomb".

Satellite picture of North Korea's nuclear test facility

Image captionSatellite photos from 2013 of North Korea's nuclear test facility - there were worries the country was ready to test weapons

North Korea has been condemned for its repeated nuclear tests.

However, it doesn't have the technology to mount a warhead on a long-range missile.

Israel is also believed to have had nuclear weapons since 1966, but it has never admitted to having them.

For more than 10 years, the UN security council has worried that Iran had been developing nuclear weapons, although a recent deal earlier this year saw the country agree to "significantly limit its sensitive nuclear activities".

The country has always argued its nuclear testing wasn't for weapons but for "civil energy use", which is what countries like Japan and Germany do, instead of relying on dwindling oil supplies.