BEIJING -  Air defense sirens wailed at 9:18 am Tuesday in Shenyang, capital of Northeast China's Liaoning province, kicking off nationwide activities marking the 81st anniversary of the Japanese invasion of northeast China.

Also on Tuesday morning, two Japanese right-wing activists illegally  landed on the Diaoyu Islands, an inherent part of Chinese territory, several days after the Japanese government illegally "purchased" the islands.

"Japanese right-wing activists illegal landing on the Diaoyu Islands is a serious provocation that infringes on China's territorial sovereignty, and, thus China has made solemn representations to Japan and demanded that the country explain its endorsement of right-wing activists," Foreign Ministry spokesman Hong Lei said later Tuesday.

The Diaoyu Islands have been China's sacred territory since ancient times - a claim supported by historical facts and jurisprudential evidence.

Japan's move has stirred great anger among the Chinese public, prompting protests against the Japanese government's "purchase" of the Diaoyu Islands in many cities across China over the past few days.

Amid this backdrop, Chinese are remembering the 81st anniversary of the "September 18 Incident," which directly preceded Japan's invasion of northeast China.

On Sept 18, 1931, Japanese troops blew up a section of the railway under its control near Shenyang, then accused Chinese troops of sabotage as a pretext for war. They bombarded the barracks of Chinese troops near Shenyang the same evening, thus starting a large-scale armed invasion of northeast China.

Four months later, Japanese troops occupied 1.28 million km of Chinese territory in northeast China, an area 3.5 times the landmass of Japan.

The incident was also followed by Japan's full-scale invasion of China and the rest of Asia, as well as the 14-year War of Resistance Against Japanese Aggression.

Remembering the event is meant to express the Chinese people's love of peace as well as send a warning to Japanese officials and right-wing activists who have denied this part of history.

As an invader who inflicted severe disaster on many Asian countries, and a country defeated in the world war II, Japan should seriously reflect on its war crimes.

However, since the 1980s, right-wing activists in Japan have repeatedly attempted to deny history, and the "nationalization" of the Diaoyu Islands is the latest and worst move in this regard.

Whether Japan can assume a proper attitude on issues such as the September 18 Incident, the Nanjing Massacre and the Diaoyu Islands issue is a test to see whether post-WWII Japan could give proper treatment to history and safeguard the peaceful development of bilateral relations.

Japan's recent moves have not only hurt the feelings of the Chinese people but have also led the country in a dangerous direction that will eventually backfire.

This year marks the 40th anniversary of the normalization of China-Japan relations. Four decades ago, leaders from the two countries, with wisdom and vision, overcame great difficulties to normalize diplomatic relations.

The development of Sino-Japanese relations over the past decades has been hard-earned, and healthy and stable bilateral ties are vital to both countries.

Tensions between China and Japan will inevitably have a negative impact on the Japanese side in many regards.

The Japanese side should take China's position seriously, listen to the just appeal of the Chinese public, stop any acts that may intensify tensions over the islands and return to the track of negotiations for the settlement of controversial issues.