China’s foreign ministry said on Friday it was concerned by the Philippines' move to resume construction work on the disputed territories in the South China Sea, saying that the planned projects infringed on Chinese sovereignty, Reuters reported.

The Manila government had agreed to halt the construction last year and had also asked other countries in the region to do so, fearing it might affect an arbitration complaint it filed against China in an international court. However, the Chinese government ignored the deadline to file a counterclaim and indicated it would not respect the court’s decision.

China has asserted its sovereignty over several islands and maritime regions in the South China Sea based on territorial lines demarcated in “historical maps.” Beijing has made it clear that it will only seek to resolve territorial disputes by discussing the claims with the concerned countries themselves. It has also refuted allegations that it is violating the U.N. Convention on the Law of the Sea.

On the one hand the Philippines makes unreasonable criticism about China's normal building activities on its own isles, and on the other announces it will resume repairs on an airport, runway and other illegal constructions on China's Spratly Islands, which it illegally occupies," Chinese foreign ministry spokeswoman Hua Chunying told Reuters. "This is not only a series infringement of China's sovereignty, but it also exposes the Philippines' hypocrisy."

However, the Philippines reportedly said its current works do not violate an informal code of conduct agreed upon by members of the Association of Southeast Nations bloc in 2002. The agreement calls upon the nations to “exercise self-restraint in the conduct of activities that would complicate or escalate disputes and affect peace and stability including, among others, refraining from action of inhabiting on the presently uninhabited islands ... and to handle their differences in a constructive manner.” The Philippine foreign ministry said the current projects, which include repairing an airstrip in the Spratly Islands, do not change the status quo of the ownership of the islands.

Other Southeast Asian countries, including Vietnam and Malaysia, have also claimed the region, which sees nearly $5 trillion of seaborne trade pass every year. Several nations, including China, Taiwan, Malaysia and Vietnam also have construction and reclamation projects underway in parts of the region they claim.

Although China has promised to resolve the disputes peacefully, it has quietly been boosting its amphibious assault capabilities and overall military budget. Other nations, including the U.S., have accused it of military “provocation.”