Vietnam and the Philippines agreed Tuesday to boost coastguard cooperation in the South China Sea, as Manila tussles with Beijing over a hotly disputed reef.

China claims almost the entire South China Sea but the Philippines, Vietnam and several other countries claim various islands, islets, reefs and shoals in the crucial strategic waterway.

Tensions have flared recently between Manila and Beijing over a series of confrontations between vessels from both countries, particularly around the Second Thomas Shoal, which Beijing calls the Ren'ai Reef.

During a state visit on Tuesday, Philippine President Ferdinand Marcos signed two deals with Vietnam, agreeing to set up a communication hotline and work on a joint coastguard committee to discuss common issues.

"The MoU (memorandum of understanding) on maritime cooperation is aimed at strengthening the understanding, mutual trust, and confidence between the two parties," Marcos's office said in a statement.

Earlier this month, China held military drills in the South China Sea as the United States and the Philippines conducted their own joint exercises in the same waters.

The drills followed a month of tense standoffs between China and the Philippines around disputed reefs in the area, which saw a collision between vessels from the two countries and Chinese ships blasting water cannon at Philippine boats.

There have been diplomatic moves to ease the tensions, with Chinese and Philippine officials holding talks a fortnight ago, and on Tuesday Marcos urged more contacts.

"We are firm in defending our sovereignty, sovereign rights, and jurisdiction against any provocations. But at the same time, we are also seeking to address these issues with China through peaceful dialogue and consultations as two equal sovereign states," he said in a statement.

During Marcos' two-day visit, Vietnam also agreed to supply up to two million tons of white rice to the Philippines per year.

The deal would ensure food security "amidst the impact of climate change, pandemics, and other external events", the statement said.

Rice is a basic staple in the Philippines, but the country cannot produce enough for itself and has been one of the world's top importers of the grain, prices of which soared to decade highs last year.

Vietnamese rice accounts for 85 percent of imported rice in the Philippines, according to official data.

Marcos also held a private meeting with Pham Nhat Vuong, CEO of Vietnamese carmaker VinFast.

The communist state's first homegrown car manufacturer said it plans to invest in the Philippines in 2024, beginning with the establishment of a network of electric car and motorcycle dealerships.

The Philippines also hopes to participate in the electric vehicle battery supply chain, working with its "abundant reserves of cobalt, copper and nickel", Marcos said.