Sri Lanka’s president has sacked his prime minister and the entire cabinet because of an alleged “conspiracy” to assassinate him.

In a televised address to the nation, President Maithripala Sirisena said investigators had discovered the name of a cabinet minister who had allegedly plotted to have him killed.

It follows several days of political turmoil in Sri Lanka.

The president first announced that he planned to fire Prime Minister Ranil Wickremesinghe last week, before ordering the suspension of Sri Lanka’s parliament on Saturday.

Within 24 hours he said the only choice left open to him was to invite his predecessor, Mahinda Rajapaksa, to take over as prime minister and form a new government.

“This information (received by investigators) contains a number of details hitherto hidden to the people,” Mr Sirisena told the country. “The informant has made a statement regarding a cabinet minister involved in the conspiracy to assassinate me.”

He did not reveal the name of the minister.

Heightened tensions had earlier turned to violence in the Sri Lankan capital Colombo. One person died and two others were wounded in a shooting at the Petroleum Ministry.

Ousted prime minister Ranil Wickremesinghe with supporters on Saturday (AFP/Getty Images)

Arjuna Ranatunga – petroleum minister under Mr Wickremesinghe prior to the mass sacking of cabinet – said a security guard had opened fire when he tried to enter the ministry building.

Mr Wickremesinghe, meanwhile, has denounced his sacking as unconstitutional.

Hundreds of his supporters gathered outside his official residence, waving party flags and denouncing the president.

Opposition politicians, supporting the newly installed prime minister, have urged Mr Wickremesinghe to vacate the official prime ministerial residence or face a forcible eviction.

Tensions have been building between Mr Sirisena and Mr Wickremesinghe for some time.

The president was critical of investigations into military personnel accused of human rights violations during Sri Lanka’s civil war, which ended in 2009.

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Mr Wickremesinghe – appointed prime minister in 2015 – had promised to hold anyone found responsible for atrocities to account.

The speaker of parliament wrote to the president on Sunday, arguing that the continued suspension of the legislative body would have “serious and undesirable consequences”.

The presiding officer said he had received a request to protect “the rights and privileges” of Mr Wickremesinghe “until any other person emerges from within parliament as having secured the confidence of parliament.”