All Japanese activities regarding the Diaoyu Islands are "illegal and invalid," a Chinese Foreign Ministry spokeswoman said Monday.

"The Diaoyu Islands are an inherent part of China's territory," spokeswoman Hua Chunying said at a daily news briefing, adding that no country challenged China's sovereignty over the islands from the 15th century to 1895.

Hua made the remarks in response to a question regarding Japanese Prime Minister Shinzo Abe's speech last week at the Center for Strategic and International Studies in Washington where he said no country questioned Japan's control over the islands during the period from 1895 to 1971.

"It is ridiculous to say so," Hua said, referring to Abe's speech.

"After the end of World War II, Japan did not fulfill its due international obligation as a defeated country in accordance with the Cairo Declaration and the Potsdam Proclamation and did not return the Diaoyu Islands to China," said the spokeswoman.

"All Japanese activities regarding the Diaoyu Islands are based on illegal theft and occupation and are therefore illegal and invalid," she said.

"No matter what the Japanese side says, they cannot hide the fact that they have illegally occupied Chinese territory," she added.

During his visit to the United States, Abe also said Japan would handle the issue in a calm manner and maintain political dialogue with China.

Hua said China's stance on the development of relations with Japan based on the "four political documents" has not changed.

The documents include the China-Japan Joint Statement signed in 1972, the China-Japan Treaty of Peace and Friendship signed in 1978, the China-Japan Joint Declaration signed in 1998 and a China-Japan joint statement on comprehensively advancing strategic and mutually beneficial relations signed in 2008.

"We hope the Japanese side will practice what it preaches, show sincerity through substantial action and make joint efforts with the Chinese side to push bilateral relations back onto a normal track," said the spokeswoman.

Regarding the Trans-Pacific Partnership (TPP) that Abe and U.S. President Barack Obama talked about during the Japanese prime minister's visit, Hua said China is open to all cooperative proposals that will help to promote economic cooperation and prosperity in Asia and the Pacific region.

Given the current situation, all sides concerned should fully consider the diversity and differences of the region and push ahead with economic integration in an open, inclusive and transparent way, Hua said. Endi