Hong Kong (CNN) -- Tensions escalated in the South China Sea region this week after China, Vietnam and the Philippines were involved in a series of potentially explosive confrontations over disputed territory.
Vietnamese officials say Chinese military and civilian ships have been intimidating their vessels near the Paracel Islands -- which are controlled by Beijing but claimed by Hanoi -- since Sunday, even accusing the Chinese of repeatedly ramming into them and shooting water cannons.
But China blames Vietnam for forcefully disrupting drilling activities, and demand that it withdraw all vessels from the area, said Yi Xianliang, Deputy Director-General of the Department of Boundary and Ocean Affairs in a press briefing yesterday.
Meanwhile, a Chinese fishing boat and its 11 crew members were apprehended on Tuesday by Philippine authorities near the Spratly Islands, another disputed region in the South China Sea.
Philippine officials say the boat was carrying a large number of endangered species and they seized the boat "to uphold Philippine sovereign rights" in the disputed waters.
"It's possible that an armed clash could occur, but not a full-fledged war. The situation with Vietnam is serious -- more serious than the situation with the Philippines," said M. Taylor Fravel, Associate Professor of Political Science at the Massachusetts Institute of Technology (MIT).
"China has controlled the northern half of the Paracel Islands since the 1950s and the southern half since 1974. Unlike the Spratly Islands, China maintains that no dispute exists over the Paracels. So we can see that China believes that its claim there is quite strong," he added.
Relations between China and Vietnam soured on Friday, when a Chinese platform began drilling for oil near the Paracel Islands. The oil rig, Haiyang Shiyou 981, is owned by state gas and oil company CNOOC.
The Maritime Safety Administration of China (MSAC) declared a three-miles exclusion zone around the rig, while military vessels have been deployed to patrol the area.
"At present, the number of escorting ships of China has reached 60, including military ships," Tran Duy Hai, Vice Chair of Vietnam's National Boundary Commission, said in a statement Wednesday.
"These vessels have intentionally hit and collided with Vietnamese law enforcement ships, including those of the Maritime Police and Fisheries Control, causing damage in human and property." (sic)
China maintains that its current drilling activities are legitimate and blame the Vietnamese for provoking conflict.
"The drilling activities of this rig are within China's territorial waters. The harassment by the Vietnamese side is in violation of China's sovereign rights," said Hua Chunying, spokesperson of China's Ministry of Foreign Affairs. She did not confirm the boat collisions.
According to CNOOC, a third of China's oil and gas resources are under the South China Sea, most of which it claims as its own, refuting rival claims from Vietnam, the Philippines, Taiwan, Malaysia, and Brunei.
In Washington, U.S. State Department Spokesperson Jen Psaki condemned China's drilling near the Paracels.
"This unilateral action appears to be part of a broader pattern of Chinese behavior to advance its claims over disputed territory in a manner that undermines peace and stability in the region," said Psaki.
China's Hua hit back saying that Chinese drilling activities "have nothing to do with Vietnam, let alone the U.S."
Meanwhile, the Philippines Department of Foreign Affairs said it will deal with the detained fishermen "in a just, humane and expeditious manner." Philippines police claimed the fishing boat was loaded with 350 endangered turtles when it was seized near an area it controls called Half Moon Shoal.
China urged Manila to "stop taking further provocative actions."
"It is possible that the Philippines may have been emboldened by the recent defense agreement reached with the United States. China and the Philippines are jostling for control of the waters in the area where the arrest occurred," said MIT's Fravel.
The arrests follow U.S. President Barack Obama's visit to the Philippines earlier this week, kicking off the annual military drills held jointly by U.S. and Filipino forces.
During the trip, the U.S. and Philippines signed the Enhanced Defense Cooperation Agreement, a 10-year security pact that gives the U.S. more military access in the region.
CNN's Dayu Zhang contributed to this report.