Somalia's most dangerous militant group said that it has killed a French hostage whom French military forces tried to rescue last weekend, Belfast Telegraph reported.

Al-Shabab said in a Twitter posting that the agent, codenamed Denis Allex, was executed on Wednesday evening.

French officials have said they believe Mr Allex was killed on the night of the rescue attempt.

Mr Allex, a French intelligence agent, was taken by the militants in July 2009 and had been held ever since.

A French raid on Friday night and early Saturday failed to rescue him, and resulted in the deaths of two French troops and 17 Somalis, French officials said.