A man stands as pigeons fly during a ceremony marking the 75th anniversary of the start of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since Japan's Nanjing massacre, also known as the "Rape of Nanking", when Japanese troops killed more than 300,000 people, local media reported. REUTERS/Carlos Barria (CHINA - Tags: POLITICS CIVIL UNREST ANNIVERSARY TPX IMAGES OF THE DAY)

A man walks along a corridor after a ceremony marking the 75th anniversary of the start of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS CIVIL UNREST ANNIVERSARY)

Skeletons of victims of the Nanjing Massacre are seen at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS ANNIVERSARY CIVIL UNREST)

Police officers stand as they attend a ceremony marking the 75th anniversary of the start of the massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS CIVIL UNREST ANNIVERSARY)

A survivor of the Nanjing Massacre (C) sounds a gong during a ceremony marking the 75th anniversary of the start of the massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS)

People attend a ceremony marking the 75th anniversary of the start of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS CIVIL UNREST ANNIVERSARY)

Schoolchildren sit down as they attend a ceremony marking the 75th anniversary of the start of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS ANNIVERSARY CIVIL UNREST)

People attend a ceremony marking the 75th anniversary of the start of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS ANNIVERSARY CIVIL UNREST)

Schoolchildren attend a ceremony marking the 75th anniversary of the start of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since the Nanjing massacre, also known as the "Rape of Nanking", in which China says Japanese troops killed 300,000 people in what was then the national capital. A postwar Allied tribunal put the death toll at 142,000, but some conservative Japanese politicians and scholars deny a massacre took place. REUTERS/Carlos Barria (CHINA - Tags: POLITICS ANNIVERSARY CIVIL UNREST)

A paramilitary policeman stands as he attends a ceremony marking the 75th anniversary of the start of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since Japan's Nanjing massacre, also known as the "Rape of Nanking", when Japanese troops killed more than 300,000 people, local media reported. REUTERS/Carlos Barria (CHINA - Tags: POLITICS MILITARY ANNIVERSARY CIVIL UNREST)

A survivor of the Nanjing Massacre reacts during a ceremony marking the 75th anniversary of the start of the massacre at the Nanjing Massacre Museum, Jiangsu province December 13, 2012. China marked 75 years since Japan's Nanjing massacre, also known as the "Rape of Nanking", when Japanese troops killed more than 300,000 people, local media reported. REUTERS/Carlos Barria (CHINA - Tags: POLITICS CIVIL UNREST ANNIVERSARY)

A man stands as pigeons fly during a ceremony marking the 75th anniversary of the Nanjing Massacre at the Nanjing Massacre Museum, Jiangsu province, December 13, 2012. China marked 75 years since Japan's Nanjing massacre, also known as the "Rape of Nanking", when Japanese troops killed more than 300,000 people, local media reported. REUTERS/Carlos Barria (CHINA - Tags: POLITICS ANNIVERSARY CIVIL UNREST)