China and the Philippines traded blame after Chinese attempts to block a Philippine supply mission to a military outpost led to two ship collisions on Sunday, escalating the territorial dispute between the countries in the South China Sea.

Both countries accused the other of illegal acts on Monday over the confrontation near Second Thomas Shoal, a sandbank inside the Philippines’ exclusive economic zone. Manila has stationed a small group of soldiers on a second world war-era former US warship that was intentionally run aground on the shoal in 1999.

According to drone footage released by the Philippine coastguard, a Chinese coastguard vessel cut in front of the bow of a small wooden ship, causing it to hit its side. A Chinese maritime militia boat later bumped a Philippine coastguard vessel, Manila said. Neither side reported injuries.