Japan has sent a submarine for the first time to join three destroyers in a military drill in the South China Sea, the Asahi Shimbun reported on Monday, a move that could provoke Beijing, which claims most of the disputed waters. Malaysia, Philippines and Vietnam are also embarking on military build-up in the disputed seas to better protect their own maritime claims and interests in the area. The Malaysian government recently announced that it would upgrade its stock of naval aircraft and helicopters, the Khmer Times reports. Beijing successfully tested its first domestically developed amphibious aircraft earlier this month, according to the South China Morning Post. The aircraft could be used to transport troops and supplies in the disputed waterway, experts said.