JAKARTA, Indonesia -- Volcanic ash from Indonesia's smouldering Mount Sinabung has blanketed parts of Medan, the provincial capital of North Sumatra, forcing residents to wear masks.

The head of the local disaster mitigation agency, Subur Tambun, said Wednesday that smoke spewing from the mountain was being carried by winds toward Medan. So far, the ash fall is not seriously disrupting daily life, he said.

Medan with a population of more than 2 million is Indonesia's third-biggest city after Jakarta and Surabaya.

TV footage showed ash blanketing parts of the city which is about 50 kilometres northeast of the mountain.

According to the Sinabung monitoring post, there were seven hot ash avalanches Wednesday that slid up to 3,500 metres southeastward. The ash cloud billowed 2,000 metres high.

The 2,460-metre volcano has spewed hot lava almost daily since its alert status was raised early this month to the highest level. More than 10,300 villagers whose homes are in the danger zone have been evacuated since then to safer areas.

Mount Sinabung is one of about 130 active volcanoes in Indonesia, which is prone to seismic upheaval due to its location on the Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin.

It has sporadically erupted since 2010, after being dormant for 400 years. An eruption last year killed at least 17 people.