GAZA CITY, Gaza Strip - The shadowy Palestinian group that kidnapped a British reporter threatened Tuesday to kill him, adding freedom for an al Qaeda-linked prisoner to its list of demands and charging that Hamas detained two of its members.

In a statement e-mailed to reporters late Tuesday, the Army of Islam said British Broadcasting Corp. correspondent Alan Johnston will be "slaughtered like a sheep'' if its demands are not met.

The message demanded that Abu Mohammed al-Maqdisi, who is being held in Jordan, be released. Al-Maqdisi is known as the spiritual mentor of the late al Qaeda leader Abu Musab al-Zarqawi.

Earlier, the group demanded freedom for Sajida al-Rishawi, an Iraqi woman sentenced to death in Jordan for her role in the al Qaeda-led triple hotel bombing in Jordan in 2005 that killed 60 people, Jordan's worst terrorist attack. Al-Rishawi, 35, was intended to be one of the suicide bombers.

In its message, the Palestinian group also called the Hamas arrest of two of its members a "declaration of war.''

In response, Ghazi Hamad, spokesman for deposed Prime Minister Ismail Haniyeh of Hamas, said, "We reject the continued captivity of Alan and we are still working to release him at the soonest possible opportunity.''

Johnston was abducted from a Gaza street on March 12. His kidnapping has been condemned by governments, human rights groups, journalists' associations and Palestinian leaders.

On Monday, the group posted a video message from Johnston on a militant website.

"I have been dressed in what is an explosive belt, which the kidnappers say will be detonated if there is an attempt to storm the area,'' he said in the recording. "They say they are ready to turn the hideout into what they describe as a death zone if there is an attempt to free me by force.''

A spokeswoman for the British Foreign Office condemned the release of the video, while Johnston's father, Graham Johnston, said his family was "most concerned and distressed at this latest development'' and pleaded for his son to be freed unharmed.