The US State Department on Sunday called on Sri Lanka's president to "immediately reconvene parliament" to allow representatives there to quell a violent constitutional crisis sparked by the prime minister's sudden sacking.

"We urge all sides to refrain from intimidation and violence," State Department spokeswoman Heather Nauert said in a statement.

"We call on the President, in consultation with the Speaker, to immediately reconvene parliament and allow the democratically elected representatives of the Sri Lankan people to fulfill their responsibility to affirm who will lead their government."

President Maithripala Sirisena fired Prime Minister Ranil Wickremesinghe on Friday and installed a former strongman as the new prime minister, triggering political chaos in the Indian Ocean nation.

Police said one man was killed and two people were injured Sunday when bodyguards for Petroleum Minister Arjuna Ranatunga, a Wickremesinghe loyalist, fired live rounds as a mob allied to the president threatened the cabinet member.

Wickremesinghe has refused to vacate the prime minister's official residence since being controversially deposed, declaring his dismissal illegal and demanding an emergency session of parliament to prove he still commands a majority.