China has called on Japan to ensure the legal rights of two activists from Hong Kong who were arrested after staging a protest at Tokyo's Yasukuni Shrine on Wednesday.

Chinese Foreign Ministry spokesman Lu Kang told a news briefing in Beijing that China has taken notice of the case and expressed concern to Japan.

"The Chinese side urges the Japanese side to properly handle the matter, ensuring the legal rights of relevant individuals," Lu said.

Civil servant lifeguard Kwok Siu-kit was arrested after setting fire to a makeshift memorial tablet at the war-linked shrine on Wednesday. Journalist Yim Man-wa, who videotaped Kwok's protest, was also detained.

The incident occurred at around 7 a.m. in front of a gate located in the middle of the Shinto shrine's premises that leads to the main shrine. There was no damage to the shrine.

The Action Committee for Defending the Diaoyu Islands, a Hong Kong-based activist group, has said both are members of the organization.

The shrine honors convicted war criminals along with millions of war dead and is often seen as a symbol of Japan's militarist past by neighboring countries, including China and South Korea.

A Japanese lawyer and staff from the Chinese Embassy in Tokyo have visited the two in custody, according to the group.

No official charges have been filed, but they could be detained for a maximum of 21 days without being charged by police during the investigation.