Volcanic lightning caught on camera in Japan

Forks of lightning flash within an ash cloud as molten lava erupts from a volcano.

This incredible weather sensation is known as volcanic lightning — and it has been caught on film by a tourist in Japan.

Filmmaker Marc Szeglat, from Germany, shot these images near the active Sakurajima volcano on the island of Kyushu between March 2 and 7.

The rare lightning phenomenon happens when hot rocks and gases collide during an eruption and produce static charges.

Szeglat also filmed the explosive shockwave which rippled through the sky afterwards.

"The lightning is very rare and does not appear in a normal ash cloud but in clouds from pyroclastic flows, which are mixtures of rock fragments and hot gases," the 47-year-old said.

"Pyroclastic flows are the most dangerous hazards on volcanoes and so I was a little bit afraid when a big one was happening in front of me, but in fact the whole experience was a great adventure."

Sakurajima, translated as Cherry Island, has been erupting on a regular basis since 1955 and is a constant danger to the nearby city of Kagoshima, which has a population of more than 600,000.