The Philippines and the United States began on Monday one of their largest joint military training exercises in years amid increasing tensions with China over its reclamation activities in the disputed South China Sea.

A total of 6,656 American soldiers, 76 aircraft and three ships from the US are participating in the Balikatan (shoulder-to-shoulder) exercises aimed at boosting operational coordination with their Filipino counterparts.

On the part of the Philippines, 5,023 troops, 13 aircraft and one ship have been assigned to the training that will include activities in the provinces of Zambales and Palawan, both near disputed territories in the South China Sea.

Just before the opening of the Balikatan, Philippine military chief General Gregorio Pio Catapang showed the latest aerial photos of the expansive reclamation and building being done by China in at least seven disputed territories.

Aside from destroying the biodiversity and ecological balance in the sea, Catapang warned: "We also believe that China's massive reclamation activities will cause tensions among claimant countries not only because it could deter freedom of navigation but also due to its possible military purposes." The Philippines has alleged that China causes economic losses of at least 100 million dollars annually due to its reclamation activities, which have destroyed an estimated 120 hectares of coral reef systems in the Spratlys islands group.

US President Barack Obama earlier expressed concern that Beijing was bullying smaller nations in the South China Sea, a key shipping lane in the Asia-Pacific region that China claims.

The Philippines has filed an arbitration case before the United Nations challenging Beijing's nine-dash line, which marks its territorial claims over nearly the entire South China Sea.

Other countries with overlapping claims to the sea are Vietnam, Malaysia, Brunei and Taiwan.