MANILA: One of the Philippines' most active volcanoes spewed huge rocks and ash early Tuesday after a 3-year calm, killing at least five climbers and trapping others near the crater, officials said.

Rescue teams were sent to Mayon volcano in the central Philippines to look for four climbers and guides trapped after the mild eruption, Albay provincial Gov. Joey Salceda said. Clouds have cleared over the volcano, which was quiet later in the morning.

The four climbers who died were struck by huge rocks, guide Kenneth Jesalva told ABS-CBN TV network by cellphone from a camp near the crater. Another man was critically injured from a group of eight that included five foreigners and three Filipino guides.

One of those killed was Filipino. The nationalities of the foreign climbers included a German and an Austrian.. No bodies have been retrieved yet.

Jesalva said he was in the group that spent the night on the picturesque mountain, known for its almost-perfect cone, when the volcano rumbled back to life early in the morning and rocks ''as big as a living room'' came raining down on them. He rushed back to the base camp to call for help.

The head of the Philippine Institute of Volcanology and Seismology, Renato Solidum, said Tuesday's eruption was normal for the restive Mayon, about 340 kilometers (212 miles) southeast of Manila. It has erupted about 40 times during the last 400 years.

In 2010, thousands of residents moved to temporary shelters when the volcano ejected ash in an 8-kilometer (5-mile) zone surrounding the crater.

Solidum said that no alert was raised for the volcano following the latest eruption and no evacuation was being planned. Climbers are not allowed when an alert is up, and the recent calm may have encouraged this week's track.