Sympathisers of the Islamic State group carried out the mass shooting this week in California that killed 14 people and wounded 21, according to a media report here.
"Two sympathisers of the Islamic State attacked a centre in San Bernardino, California, opening fire inside the location, killing 14 people and wounding 21," a statement from the pro-IS Arabic-language news agency Aamaq said.
Aamaq is active in IS-run territories but is not considered to be the jihadist group's mouthpiece and does not claim attacks on its behalf.
"This operation comes after the bloody Paris attacks, which were carried out by fighters from the state... which caused the killing of dozens, and after a martyrdom-seeking operation on presidential security in the centre of the Tunisian capital," it said.
Aamaq did not say what the motive was.
US media, quoting law enforcement officials, have said that while there was no evidence IS directed Syed Farook and his wife Tashfeen Malik to carry out the attack on a party held by Farook's employer, it appears the pair were inspired by the group.
The US Federal Bureau of Investigation said Friday the shooting is now being investigated as an "act of terrorism".