MANILA- Malacañang on Sunday defended the visit of Defense Chief Delfin Lorenzana and other military officials to Pag-asa Island in the West Philippine Sea, saying it is lawful under international law.

Presidential Spokesman Ernesto Abella on Sunday said maritime patrols over the disputed waters are not new and that the patrols allow Manila to reach its municipality in the island.

"The Philippines has long been undertaking customary and routine maritime patrol and overflight in the West Philippine Sea which are lawful activities under international law. Such flights will likewise enable us to reach our municipality," he said in a statement.

China last Friday challenged 2 Philippine planes, one of which was carrying Lorenzana, as it approached Pag-asa Island.

Beijing's Foreign Ministry Spokesperson Lu Kang said China is "gravely concerned" and "dissatisfied" with Lorenzana's visit.

• READ: China 'gravely concerned and dissatisfied' with Lorenzana visit to Pag-asa Island

Abella however said there was nothing unusual in Lorenzana's visit to the island which was part of Philippine territory.

"The visit of the Department of National Defense and the Armed Forces of the Philippines to Pag-asa Island is part of the efforts to improve the safety, welfare, livelihood of Filipinos residing and living in the municipality of Kalayaan which is part of the province of Palawan," Abella said.

The defense chief flew to Pag-asa Island last Friday to check on its facilities, some of which were in dire need of repair.

He vowed to upgrade Manila's facilities in the island after seeing how these paled in comparison with those built by China on its artificial islands.

Manila and Beijing are slated to conduct bilateral talks next month.