The Philippine Coast Guard has accused its Chinese counterpart of steering one of its ships within metres of a Filipino patrol vessel in the disputed South China Sea, “breaking international rules” and risking a collision.

The incident happened on March 2 near the contested Scarborough Shoal – one of the region’s richest fishing grounds and a flashpoint between the two countries – but was only made public on Sunday.

It was the fourth time in the past year that a Chinese coastguard vessel had conducted “close distance manoeuvring” near the shoal, the Philippine Coast Guard (PCG) said in a statement.

China laid claims to Scarborough in 2012 following a tense standoff.

The Philippines continues to patrol the waters around the shoal, which is inside its Exclusive Economic Zone.

“The behaviour of the involved [China Coast Guard] vessels increased the risk of collision with four of our capital ships,” PCG chief Admiral Artemio Abu said.

In the March 2 incident, the PCG said the Chinese vessel came within about 19m of its patrol boat, which was in “clear violation” of the 1972 International Regulations for Preventing Collisions at Sea.

The PCG has referred the matter to the foreign ministry, which recently summoned China’s ambassador over a separate incident involving a Chinese navy ship “lingering in the Philippines’ archipelagic waters”.

Abu said his agency was under government orders to maintain patrols near Scarborough Shoal, where Filipino fishermen continue to fish.

There was no immediate comment from the Chinese embassy or the Philippine foreign ministry.

Tensions between Manila and Beijing over the South China Sea, which China claims almost its entirety, have intensified in the final year of President Rodrigo Duterte’s term in office.

Beijing has “ignored” a 2016 international tribunal decision that declared its historical claim over most of the South China Sea to be without basis.

Duterte set aside the ruling in exchange for promises of trade and investment, which critics said have not materialised.

But in November he hardened his stance, expressing outrage after Chinese coastguard ships fired water cannon at Filipino boats.

This latest incident comes on the eve of the biggest-ever war games between the Philippines and the US.

Recent manoeuvres between the longtime allies have focused on potential conflict in the South China Sea, where Brunei, Malaysia, Taiwan and Vietnam also have competing claims.