A rescue helicopter en route to an erupting volcanic crater in Indonesia's Central Java province crashed on Monday (3 July). Eight people on board the copter were instantly killed, the National Search and Rescue Agency said.

Zulhawary Agustianto, spokesman for the rescue agency, told The Jakarta Post that the copter is suspected to have crashed after hitting a cliff in an area called Canggal in Candiroto district.

The copter crashed in Temanggung area leaving four crew members and four rescuers dead, Major General Heronimus Guru, operational director of the rescue agency said.

The crash took place soon after the helicopter departed from Central Java's provincial capital of Semarang at around 4pm local time (10am BST). It was headed to the Dieng Plateau where an active volcanic crater erupted around noon local time.

The volcanic crater, Sileri Crater, is a famous tourist spot in the country and several people present around the crater at the time of eruption were injured as cold lava and smoke spurted out of the active volcano.

The National Disaster Mitigation Agency reportedly said there were at least 17 tourists at the crater when it suddenly started oozing out smoke and lava. Ten people sustained injuries, including bruises and a fractured arm. They were immediately taken to a nearby community health centre to receive treatment, the agency added.

Sutopo Purwo Nugroho, spokesman for the disaster mitigation agency, said in a statement that the sudden eruption at the volcanic crater was caused by underground gas pressure. The increasing pressure resulted in the explosion that sent out a mix of steam, water, ash and mud.

"The authorities asked visitors and residents to vacate the area because there was potential for the crater to erupt for a second time," Sutopo added.

Central Java police chief inspector general Condro Kirono said nearly 100 rescue personnel had reached the crash site and were tackling the situation.

Sileri Crater is reportedly the most active and dangerous crater in the volcanic Dieng Plateau. It has recorded six eruptions between 1939 and 2009, according to a local disaster management agency.