The Japanese Government is planning to amend legislation and rules governing unmanned aircraft to tackle potential threats posed by them such as terror attacks.

The decision by the government comes after a small drone landed on the roof of the Prime Minister Shinzo Abe’s office.

Japan chief cabinet secretary Yoshihide Suga was quoted by Bloomberg as saying: "There is a risk that unmanned aircraft could be used for a terrorist attack at events such as the Olympics or the G7 summit.

"This could potentially lead to more regulations on unmanned aircraft."

"We have to quickly prepare legislation and rules."

According to Tokyo Metropolitan Police Department, the propeller-driven drone is equipped with a small camera and a bottle of unidentified liquid, raising concerns that such activity might be a part of a terrorist attack.

The investigation team identified traces of radioactive cesium near the drone, and is currently testing the liquid in the container for radioactivity.

Sophia University professor of politics Koichi Nakano said: "This could potentially lead to more regulations on unmanned aircraft.

"Much depends on whether the radioactive material found indicates this was an attack."

Japan’s public broadcaster NHK reported the 20in drone as DJI’s Phantom series aircraft.

In January, a Phantom-series drone crashed onto the grounds of the White House in the US. The incident prompted for tighter regulations on civilian use of unmanned aircraft in the country.