The BBC has witnessed Chinese vessels blocking Filipino supply boats to an outpost in the South China Sea.

The incident took place as two Philippine coast guard ships – one of which the BBC was aboard – and two tiny commercial boats made their way to the Second Thomas Shoal.

They were met by a ship marked as the Chinese Coast Guard that was five times bigger than the commercial boats.

It resulted in a standoff which lasted several hours.

It comes as tensions between Manila and Beijing are high, after the Philippines coast guard cut China’s barriers in disputed waters earlier last month.

Manila resupplies its outpost in the Second Thomas Shoal, in the Spratly Islands, every month to reinforce its economic rights to waters that are both rich in fish and mineral resources.

Beijing claims almost the entire South China Sea, including the Spratlys, which is also claimed in part by the Philippines.

The incident took place on Wednesday, the second day of a three-day mission to the Second Thomas Shoal. The journey proceeded in rough seas due to a then-oncoming typhoon and the seasonal monsoon.

A little past dawn, the Filipinos were met by what appeared to be the Chinese Coast Guard, as well as two blue militia vessels with Chinese markings.

The two Philippine Coast Guard ships were escorting the Filipino commercial boats which carried supplies that are good for roughly one month.

When the two countries’ vessels encountered each other, the Chinese ships sent radio challenges to the Filipinos, asking them to leave. When the Philippine ships refused, the Chinese aligned themselves in a box shape to block them.

The two Filipino commercial ships got past the blockade because of their small size, a strategy that has worked in recent months.

But the two Philippine Coast Guard ships were too big to pass and at one point got within a few metres of the Chinese ships. They were so close that their crews took photos of each other. A Philippines military plane was also seen flying overhead.

The Philippine ships turned back at sundown when they confirmed that the supplies had been delivered and that the two commercial ships were safely on their way back to port.

All four vessels made it back to port, several hours’ drive north of the capital Manila on Thursday.

Aside from sailing dangerously close to Filipino ships, China has been accused of firing water cannons and shining lasers on Philippine ships to drive them away.

Manila also claims that China deploys militia ships to boost its coast guard patrols in the disputed sea.

In 2016, an international arbitration court at The Hague ruled that China’s vast sea claims had no basis, acting on a case brought forth by Manila. Beijing has refused to recognise it.

In recent months, tensions have been especially high between China and the Philippines, which recently strengthened military ties with the US, Beijing’s chief rival for influence in the region.

The Chinese coast guard condemned the latest resupply mission, saying the Filipinos entered what it calls the Nansha islands without its permission. The Philippines calls it Ayungin Shoal, after a small fish that is a local delicacy.