Somali insurgents linked to al Qaeda have demanded that Kenya release all Muslims held on terror charges within three weeks, failing which they said they would kill their Kenyan hostages.
Al Shabaab said it killed French hostage Denis Allex last week to avenge what it called France's growing persecution of Muslims and its military operations against Islamists, including in Mali.
The kidnapping of dozens of hostages at a gas plant in Algeria by Islamist fighters last Wednesday and al Shabaab's claim illustrate the potential fallout from France's battle against loosely allied bands of al Qaeda-inspired rebels in Africa.
France sent troops to Mali earlier this month after Islamist fighters in northern Mali advanced south and the government in the capital Bamako appealed for help.
Al Shabaab (@hsmpress) tweeted a link to a video of two Kenyan civil servants, who were seized from the frontier county of Wajir a year ago, telling the Kenyan government their lives were in grave danger.
It then tweeted that Kenya had to release all Muslim prisoners held on "so-called terrorism charges in Kenya" and "secure the release of Muslims extradited to Uganda for terrorism charges".
"Kenyan government has 3 weeks, starting midnight 24/01/2013 to respond to the demands of HSM if the prisoners are to remain alive," the group posted on Twitter.
Kenyan officials were not immediately available for comment.
Titled "KENYA POWS: FINAL MESSAGE", the video released by the insurgents featured Mule Yesse Edward, a local administrator, and Fredrick Irungu who works with ministry of immigration.
Both were captured last January when the militants crossed the border into Kenya and attacked an administration police post in Wajir, killing several police officers.
The video also contained a still photograph of four other Kenyan hostages who were not identified. Yesse, who spoke in the video, said all the Kenyan hostages held by the group were at risk if Kenya did not meet the rebels' demands.
Kenya has held several suspects due to links with al Shabaab in Nairobi and in the coastal city of Mombasa.
It also extradited several suspects to Uganda after a 2010 suicide bombing, claimed by al Shabaab, in Kampala that killed several people.
Nairobi sent its troops across the border to pursue al Shabaab rebels in October 2011 after the insurgents kidnapped western tourists and Kenyan security forces on Kenyan soil.