"I strongly condemn the terrorist attack targeting the residence of Iraqi Prime Minister al-Kadhemi," Biden said in a statement.

"I am relieved the Prime Minister was not injured and commend the leadership he has shown in calling for calm, restraint, and dialogue to protect the institutions of the state and strengthen the democracy Iraqis so richly deserve."

Kadhemi escaped unhurt when an explosives-packed drone struck his Baghdad residence early Sunday. But the attack marked a substantial escalation in the country's post-election turmoil.

The prime minister's office described the attack as a "failed assassination attempt," while Iraqi President Barham Salih called the strike, which was not immediately claimed by any group, an attempted "coup against the constitutional system."

Biden said that "the perpetrators of this terrorist attack on the Iraqi state must be held accountable," as he condemned "in the strongest terms those using violence to undermine Iraq's democratic process."

The US leader said he instructed his national security team "to offer all appropriate assistance to Iraq's security forces as they investigate this attack and identify those responsible."