Meanwhile, the FBI said that it had recovered the remains of two kidnapped US contractors in Iraq.
The agency identified the contractors as Ronald Withrow and John Roy Young.
Mr Withrow worked for JPI Worldwide when he was kidnapped in January last year. Mr Young worked for Crescent Security Group when he was kidnapped in November 2006. The FBI says the investigation into the kidnappings is continuing.
Rear Admiral Gregory Smith, a US military spokesman in Baghdad, said the rockets fired into the Green Zone, also known as the International Zone, were Iranian-made and supplied by the Quds Force, an elite unit of Iran’s Revolutionary Guards.
The US military has blamed Iran for arming and funding Shiite extremists to fight American forces in Iraq. Tehran denies the allegation.
US Embassy spokesman Philip Reeker said two government employees – an American and a Jordanian – were seriously injured and six other people required medical attention after Sunday’s volley of rocket attacks.
Local hospital and police officials said at least 12 Iraqis were killed and 30 more were wounded in rocket or mortar blasts that apparently fell short after being aimed at the Green Zone from scattered areas of eastern Baghdad.
Admiral Smith said: “We have assessed the rockets fired into the International Zone and those that struck neighbourhoods nearby were the responsibility of Iranian-backed special groups.”
The military uses the term special groups to refer to Shiite extremists continuing attacks despite a ceasefire order by radical Shiite cleric Muqtada al-Sadr to his Mahdi Army militia.
