Philippine tour guide Roel Llarena recalled Wednesday how a mountain hike turned into a nightmare when the volcano he was climbing began spewing out giant rocks, killing five of his companions.

"I stood there frozen. I couldn't believe what was happening, I didn't know what to do. It was like a scene from hell," he told AFP, after surviving the giant ash explosion at Mayon volcano on Tuesday.

Llarena, 33, was one of the Filipino tour guides leading a group of foreigners up the 2,460-metre (8,070-foot) Mayon when the picturesque volcano suddenly shot a column of hot ash into the air.

The volcano, famed for its near-perfect cone, has a history of deadly eruptions. But it was not showing signs of activity when the tour group ascended, leading many to think it was safe.

"The tourists were all very nice and we were exchanging stories with them the previous night. I can't believe this all happened, especially when the night before we were just all having fun," Llarena said by phone.

The group was climbing the mountain when rain started to pour down. Recognising the danger, Llarena and the others began to turn back only to see a column of ash shoot from the cone.

The hikers took cover behind a huge rock as boulders, some as large as minivans, began tumbling towards them and carried some people to their death.

Llarena said a fellow guide, Nicanor Mabao, saved an Austrian woman by grabbing her by her bag. But three Germans, a Spanish woman and a Filipino guide -- Llarena's brother-in-law -- were killed by the cascade of rocks.

Rescue teams recovered the five bodies but bad weather prevented helicopters from landing on the mountain and the body bags were carried down by hand.

A Thai tourist who went missing during the ash explosion was found with minor injuries on Tuesday, local officials said.

Volcanologists described the eruption as a 73-second "steam-driven minor explosion" that was not expected to be repeated anytime soon.

Chief state seismologist Renato Solidum said the explosion was triggered when the rainwater made contact with hot ash deposits on the crater mouth.

The province's governor Joey Salceda said some tourists were drawn to the volcano 330 kilometres (200 miles) southeast of Manila, because of the danger.

"Mayon volcano is an enigmatic personality. The more she does this, the more they will come. The more the danger, the more the tourists," he told reporters.

But Llarena will not be guiding them any more.

"After this I'm definitely not going back to Mayon. I curse Mayon volcano. I vow never to climb it again," he said.