China asserted its right to monitor airspace and waters near its islands in the South China Sea on Thursday in response to reports of an exchange between the Chinese navy and a US surveillance plane.

The remarks came after a CNN news crew on a US Air Force P8-A Poseidon surveillance plane on Wednesday reported that it heard the Chinese navy warn the plane to leave the area eight times as it flew over a Chinese island.

The CNN report said the US crew responded that they were flying through international airspace, to which the Chinese dispatcher answered: "This is the Chinese navy. We urge you to leave."

Foreign Ministry spokesman Hong Lei said he wasn't aware of the incident, but reiterated Beijing's indisputable sovereignty over the Nansha Islands and surrounding waters in the South China Sea.

"China has the right to monitor the relevant airspace and waters to protect the country's security and prevent accidents at sea," he said.

He urged other countries to "abandon actions that may complicate and exaggerate controversies".

When asked why the US had allowed the CNN news crew to be on the surveillance plane, Daniel Russel, US assistant secretary of state for East Asian and Pacific affairs, said on Thursday that it's for the purpose of transparency. "We want to share what we do and share what we see," he told a press conference at the Foreign Press Center in Washington.

He defended the US close-in reconnaissance by military vessels and aircraft as being in international waters and airspace. "We will continue to fully exercise our rights in international space," he said. Chinese officials have raised repeatedly over the years their opposition to the US close-in reconnaissance along the Chinese coast. Some US experts on bilateral relations have also described such US actions as "provocative."

Russel called Chinese land reclamation on the islands and reefs in the South China Sea as "destabilizing" and said Secretary of State John Kerry expressed serious US concern when he met with Chinese leaders in Beijing last week. He said that Kerry underscored that tensions generated in the South China Sea by China's action do have an impact on US-China bilateral relations.

Chinese officials, such as Chinese Ambassador to the US Cui Tiankai, have publicly expressed dissatisfaction with the US for remaining completely silent when other countries, such as Vietnam and the Philippines, built more outposts in the South China Sea, some on islands that belong to China.

Yin Zhuo, a senior expert on the Chinese navy, said the US armed forces always cite "freedom of navigation" when intruding into other countries' waters and airspace.

Hong commented on remarks by US Deputy Secretary of State Antony Blinken about China's land reclamation operations on its islands in the South China Sea, saying the work is in line with China's sovereignty and aims to provide a civilian service that will benefit other countries.

Blinken said on Wednesday that the work risks provoking tension that could lead to conflict.

Hong urged the US to abide by the principle of not taking sides over the South China Sea, and said its groundless remarks will "encourage repeated provocations from certain nations".

Also on Thursday, Shen Jinke, a spokesman for the People's Liberation Army air force, said the aviation division has for the first time flown across the Miyako Strait, the open sea between Japan's Miyako and Okinawa islands, for deep-sea training in the west Pacific.