Japan has urged China to ensure the safety of four Japanese nationals detained since last week in Hebei Province and "handle the case swiftly from a humanitarian viewpoint," the Japanese Embassy in Beijing said late Sunday.

Hidehisa Horinouchi, a minister at the embassy, filed the request with Qiu Xuejun, deputy director general in the Chinese Foreign Ministry's Department of Consular Affairs, by telephone Sunday night, the embassy said in a news release.

Horinouchi asked for continued access to the men, such as visits by the local Japanese consul and interviews with lawyers.

All four are employees of construction company Fujita Corp. They were detained Sept. 20 for allegedly entering a military zone in the outskirts of Shijiazhuang, Hebei Province, without permission and videotaping facilities there.