TOKYO - A group of 40 Chinese who say they were wounded or lost relatives as a result of Japanese bombing of the city of Chongqing before and during World War Two filed a suit against the Japanese government on Thursday.

The plaintiffs, mostly in their 70s and 80s, want an apology and 10 million yen ($84,920) each in compensation, Kyodo news agency and other media reported.

The plaintiffs say the repeated bombings of the southwestern Chinese city, formerly known as Chungking, between 1938 and 1943 were war crimes that violated the Hague Convention, which banned any kind of attacks on unarmed cities, Kyodo said.

A new study by a Chinese group showed that about 23,600 people were killed and 31,000 wounded in the raids, Kyodo said.

Japan's ties with China have long been frayed by disputes stemming from Japan's invasion and occupation of parts of China from 1931 to 1945.

Ties are now in their worst shape in decades, particularly as a result of Japanese Prime Minister Junichiro Koizumi's annual visits to Tokyo's Yasukuni Shrine, where 14 convicted war criminals are honoured along with Japan's war dead.

Dozens of compensation claims related to Japanese aggression before and during World War Two have been filed in Japan against the government or companies, but most have been rejected.

In the latest ruling, a Japanese court on Wednesday rejected claims by 45 elderly Chinese who were taken to Japan during World War Two for forced labour. They were seeking redress and apologies from the government and two private firms.

The government insists that the issue of war reparations was settled by the 1951 San Francisco Peace Treaty that formally ended the war and by later bilateral treaties.

It says all wartime compensation issues concerning China were settled by a 1972 joint statement establishing diplomatic ties.