Image copyright AFP

Three people connected to one of the San Bernardino attackers have been arrested over alleged marriage fraud.

The brother and sister-in-law of gunman Syed Rizwan Farook were among those held after raids in California.

The third person arrested is the wife of Enrique Marquez Jr, a friend of Farook who faces charges himself in relation to the deadly attack.

Fourteen people were killed when Farook and his wife, Tashfeen Malik, opened fire at an office party in December.

The killings were described by authorities as the deadliest terror attack on US soil since 9/11.

The three arrested are being held on charges of conspiracy, marriage fraud and false statement charges, officials said.

Mariya Chernykh, a Russian citizen, is accused of marrying Enrique Marquez in an immigration scam, the US Department of Justice said in a statement.

Her sister is married to Farook's brother and all three face conspiracy charges connected to the marriage.

The raids on Thursday were conducted at homes in the cities of Corona and Ontario.

Farook and Malik were killed hours after the attacks, in a police shoot-out following a car chase.

Mr Marquez was arrested earlier this year. He denies plotting terrorism and supplying weapons.