Shrubbery outside the Ministry of Economy, Trade and Industry was set on fire, scorching the wall of a nearby subway station building, police said.

They arrested a 78-year-old anti-nuclear activist for allegedly starting the blaze Monday and damaging private propery.

The suspect, Taichi Masakiyo, heads a citizens' group that opposes the use of nuclear power.

His group was camping out on the ministry's grounds in central Tokyo from the 2011 start of the Fukushima nuclear crisis until they were booted out last summer. METI promotes the nuclear power industry.

The fire left a burn mark measuring 15 cm by 1 meter on the wall of the surface building for Kasumigaseki Station. The shrubbery is maintained by subway operator Tokyo Metro Co.

According to the police, Masakiyo's anti-nuclear group had been maintaining three tents on METI property.

Last August, the tents were removed by Tokyo District Court officials after the Supreme Court ruled in July that the group must strike the tents.

The group has continued its protest activity.