The fate of three Japanese civilians taken hostage by an armed group in Iraq remained unknown Monday morning -- more than a full day after a statement by the kidnappers promising to release them within 24 hours was broadcast.

The three are being held near Fallujah, west of Baghdad, and a negotiator has told the Japanese government that they remain safe, a government source said early Monday, acknowledging that an unidentified person is serving as a go-between with the kidnappers.

Meanwhile, a person claiming to be a mediator told an Arab television that the kidnappers have renewed their threat to kill the hostages unless Japan pulls out its troops from Iraq. Japanese officials, however, said credibility of the man's remark is questionable.