BEIJING—China allowed a brief protest outside the Japanese Embassy and sounded sirens in several cities Saturday as it commemorated the start of Japan’s 1931 invasion amid official unease at Tokyo’s new diplomatic and military ambitions.The official commemorations were the biggest to date and come at a time of rising anti-Japanese sentiment, stoked by a communist government that regards Japan as its rival for regional superpower status.In Beijing police let 20 protesters gather outside the Japanese Embassy holding banners opposing Tokyo’s bid for a permanent seat on the UN Security Council and its claim to a disputed island chain.“The Chinese people who have fully suffered the wounds of Japanese militarism must strain every nerve to be vigilant!” one protester, Zhang Jianyong, said through a loudspeaker.The protesters marched away after a few minutes waving Chinese flags and singing the national anthem. Zhang sounded a hand-cranked siren at 9:18 a.m.—a time that represented the September 18 date of the 1931 invasion—but it was quickly confiscated by police.Sirens sounded in a dozen cities in China’s northeast from 9 a.m. to 9:10 a.m., the official Xinhua news agency reported. The government said similar events were planned in more than 100 cities throughout the country.The 1931 attack on the northeastern city of Shenyang, then known as Mukden, led to the Japanese occupation of China’s northeast. That was followed in 1937 by the occupation of much of China that lasted until Tokyo’s 1945 surrender at the end of World War II.Many Chinese resent what they regard as Japan’s failure to atone for its aggression and millions of Chinese deaths.The communist government keeps alive memories of the “Mukden incident” through state media and schoolbooks and uses the date to rally nationalism. It was designated “National Defense Education Day” four years ago, opening the way for formal commemorations. Many cities held theirs on Saturday for the first time.State media called on participants to chant, “Do not forget national humiliation!”Hundreds of people visited Shenyang’s monument to the invasion, Xinhua reported. Photos on its website showed children in the nearby city of Changchun saluting in front of a stone slab commemorating the attack.In Beijing, retired Defense Minister Cao Gangchuan and hundreds of soldiers attended a ceremony at the Chinese capital’s World War II monument. State television said several hundred students took part in a flag-raising ceremony at elite Tsinghua University—the alma mater of President Hu Jintao.In Hong Kong a dozen demonstrators marched to the Japanese Consulate to demand an apology for the invasion and compensation from Japan.“Oppose Japan’s military imperialism,” read a banner upheld by the activists, who chanted slogans and carried a large poster showing Japanese soldiers killing Chinese civilians.Chinese nationalism, especially among the young, has surged along with the country’s economy and international influence.--AP