Lombok - An active volcano has erupted in Indonesia, spewing ash and lava at least 1,500 metres into the sky, damaging crops but not threatening villagers, an official said today.

Mount Baru Jari on Lombok island, near Bali, has been active for several months but yesterday's eruption was "big," the island's volcano monitoring official Mutaharlin told AFP.

"From yesterday evening to early today, the volcano erupted three times and was accompanied by tremors. The first eruption spewed ash and lava 1,500 to 2,000 metres high," he added.

Lava flowed into a lake, pushing its temperature to 35 degrees Celsius, up from 21 degrees Celsius, Mutaharlin said.

"The smoke had spread as far as 12 kilometres and dozens of acres of crop land were covered in ash," he said.

"But the eruptions haven't reached dangerous levels yet, so we're not evacuating villagers," he added.