Rig HD-981, deployed last month by the China National Offshore Oil Corp., is about 100 miles off the coast of Vietnam in the South China Sea.
The rig has been a source of contention between the Chinese and Vietnamese governments, which both claim the maritime territory as their own.
Vietnamese state television broadcast footage Thursday showing a Chinese vessel ramming a Vietnamese fishing boat last week, causing it to capsize.
Chinese Foreign Ministry spokesman Hong Lei said Thursday the Chinese vessels were less than 20 miles away from an island claimed by Chinese authorities, though the Vietnamese vessels had to travel more than 150 miles to reach the site.
"So which side initiated the clash at the site? Which side created tension at the site?," he said during his regular press breifing. "This is very clear."
No injuries were reported in the latest clash. Dang Van Nhan, the captain of the capsized Vietnamese vessel, told Voice of America last week the Chinese were "trying to kill us."
The U.S. government, which owns VOA, says it has no stance on territorial claims, but accuses the Chinese side of provocation.