A group of hikers have had a lucky escape after Indonesia’s most active volcano erupted when they were cooking breakfast at the foot of Mount Merapi.

Shopan Pangestu filmed the moment the volcano spewed sand and pyroclastic material, sending an ash column as high as 5500 metres into the sky on Friday.

He posted the video on Instagram and later told Reuters he and his friends first heard “rumbling” sounds and then a “roar”.

Mount Merapi spews volcanic materials from its crater as seen from Klaten, Central Java, Indonesia. Picture: AAP (AAP)

Campers were having breakfast when the volcano erupted. Picture: Instagram (Supplied)

He said he was worried for one of his friends who had climbed to the top of the mountain.

“We all left our things, heading away north from the mountain,” Pangestu said.

“There was a black cloud and we were right under it. Fortunately the direction of the wind was heading south, and the black cloud was southward, not towards us."

The sudden eruption was accompanied by a rumbling sound with medium to strong pressure, Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said.

Shopan Pangestu filmed the moment the volcano spewed sand and pyroclastic material. Picture: Instagram (Supplied)

There were no immediate reports of death or injuries.

The 2968-metre mountain between Yogyakarta and Central Java provinces is the most active of Indonesi’s 500 volcanoes.

Its last major eruption was in 2010, when it killed 347 people and caused the evacuation of 20,000 villagers.

Villagers walk as Mount Merapi is seen in the background in Pemalang, Central Java. Picture: AAP (AAP)