Indonesia's Mount Merapi, one of the world's most active volcanoes, erupted on Tuesday, spewing lava more than two kilometres from the crater.

Dramatic images of lava pouring from the volcano's smoking crater were published by the government-run Merapi Volcano Observatory.

Dozens of small tremors related to Merapi's eruption were recorded on Tuesday, according to the Centre for Research and Development of Geological Disaster Technology (BPPTKG), a government agency that monitors the volcano.

"Merapi's activity slightly increased over the last few days... but these kinds of increases often occur in Merapi," said BPPTKG head Agus Budi Santoso.

Clear weather meant people could easily see the eruption pouring from the volcano, he said.

Merapi, which sits just 28 kilometres north of the provincial capital Yogyakarta, is closely monitored by the agency.

Authorities implemented a restriction zone of seven kilometres in 2022 following a risk assessment for the surrounding villages.

Lava from Merapi's eruption on Tuesday fell well within that zone, Santoso said.

Merapi's alert level, which has been kept at the second-highest mark since 2020 following increased volcanic activity, has remained unchanged, Santoso said.

The volcano's last major eruption in 2010 killed more than 300 people and forced the evacuation of some 280,000 residents.

It was Merapi's most powerful eruption since 1930, when about 1,300 people were killed. (AFP)