Image copyright Reuters Image caption Japanese police are also probing how a drone landed on the prime minister's office

Japanese authorities have detected an unusually high level of radiation around playground equipment in a Tokyo park, report local media.

The park, in the Toshima ward in central Tokyo, has been fenced off.

Authorities recorded up to 480 microsieverts per hour at one spot - nearly half the recommended annual limit of exposure for a person.

The incident comes days after a drone with traces of radiation landed on top of the prime minister's office.

The drone at Prime Minister Shinzo Abe's office was discovered on Wednesday morning, carrying a small bottle with the radioactive symbol.

Tests found it was carrying a small amount of radioactive caesium, reported Kyodo news agency.

Public concern

Japan's NHK reported that local officials had received a call about suspected radioactivity at the Tokyo park on Wednesday.

Following two rounds of testing, officials found high levels of radiation on a section of the playground equipment.

Authorities believe that the radiation could be coming from something buried underneath the park.

Yukio Takano, the mayor of Toshima district, said the risks were minimal, but that the area was being cleaned to reassure local residents, AFP news agency report.

According to the International Commission on Radiological Protection recommendations, members of the public should not be exposed to more than 1000 microsieverts per year.

Japan has seen heightened concern over radiation since the 2011 failure of a nuclear plant in Fukushima following an earthquake and tsunami, which led to leaks of radioactive water,

All of Japan's nuclear reactors were taken offline following the incident. Recent attempts to restart some of them have been met with vocal opposition by local residents.