Blast close to US base in Japan

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There has been a small explosion near a United States' military base south of the Japanese capital, Tokyo, US officials have confirmed.

The blast happened outside the Camp Zama army base around 40km (25 miles) south-west of Tokyo.

Police found two pipes believed to have contained explosives close to the camp, Kyodo News agency reported.

A Pentagon official said that there were no reports of injuries caused by the blast.

"A small explosion was heard in the vicinity of the base," said Air Force Maj David Smith.

"It did not occur on the base."

Residents said the explosion took place at around 2300 local time (1600 GMT).

The US military has more than 40,000 troops in Japan stationed on several sizeable bases under a bilateral security deal.

Some Japanese residents oppose the presence of the bases, but attacks are rare.

In 2002, two blasts occurred outside Camp Zama, an attack police blamed on extremists.