The Chinese jets came within 50 feet of the U.S. aircraft at one point during the incident, which took place Tuesday, the official said.
However, Beijng said the EP-3 reconnaissance aircraft flew close to China's island province of Hainan and its jets "kept a safe distance throughout, without taking any dangerous actions."
"It needs to be pointed out that American aircraft have constantly entered China's coastal waters conducting reconnaissance, which has posed a serious threat to China's maritime and air safety," Hong Lei, Ministry of Foreign Affairs spokesman, said at a regular press briefing Thursday.
"We hereby ask the U.S. immediately to stop these actions so as to avoid the recurrence of such incidents," he added.
The South China Sea is home to a messy territorial dispute
and China has been boosting its presence in the already tense region.
Beijing has previously warned U.S. warships
and military aircraft to stay away
from the islands it controls.
Pentagon: They have our attention
"We have made progress reducing risk between our operational forces and those of the People's Republic of China by improved dialogue at multiple levels under the bilateral Confidence Building Measures and the Military Maritime Consultative Agreement," Capt. Jeff Davis, a Pentagon spokesman, said.
"Over the past year, we have seen improvements in PRC actions, flying in a safe and professional manner," he said. "We are addressing the issue through the appropriate diplomatic and military channels."
A separate defense official told CNN this type of incident is not something the U.S. military frequently sees in that region with Chinese aircraft. Incidents with Russian aircraft in the Black Sea that have been well documented over the past year are much more common.
This is an incident that "definitely has people's attention" at the Pentagon, the second official said.
"This is potentially part of a disturbing trend line as the Chinese try to push their military envelope into greater parts of the sea surrounding their mainland," Sen. Chris Murphy, a Democrat who serves on the Senate Committee on Foreign Relations, told CNN's Wolf Blitzer.
Murphy said that it is important that the U.S. does not overreact to these types of occurrences, which have recently involved Chinese and Russian militaries.
"What the Chinese and the Russians are trying to do is to provoke us into some kind of action that will feed into their domestic narratives, both in China and in Russia," Murphy said.