China started drilling operations near the Xisha Islands in the South China Sea in early May. The Vietnamese government said the program is a violation of its sovereignty.
In a statement Sunday, the Chinese Ministry of Foreign Affairs said the Vietnamese have harassed its vessels in the area repeatedly since drilling operations began.
"There were as many as 63 Vietnamese vessels in the area at the peak, attempting to break through China's cordon and ramming the Chinese government ships for a total of 1,416 times," the statement said.
The ministry said Chinese oil companies have been working in the region for the past 10 years. Drilling operations near the islands, it said, are part of a "routine" exploration process.
Vietnamese officials have said they have a right to defend their national interests in the region. Hanoi last week said Chinese vessels around the rig are harassing nearby Vietnamese ships on a daily basis and have since expanded their zone of protection around the rig by about 45 percent.