Sri Lanka's largest party vowed to mount a full scale challenge to the "tyrant" President Maithripala Sirisena after the shock sacking of parliament that left the country teetering on the edge of further civil unrest.

President Maithripala Sirisena dissolved his country’s parliament at midnight on Friday and called snap elections, risking a return of a revolt that saw one a protester die from gunshots fired at protesters.

The United National Party (UNP), which holds the most seats in parliament, said the president had "kicked the constitution in the teeth" with his latest move.

They vowed on Saturday, "We will fight in the courts, we will fight in parliament and we will fight at the polls."

Mark Field, the British minister of State for Asia and the Pacific, said: "As a friend of Sri Lanka, the UK calls on all parties to uphold the constitution and respect democratic institutions and processes."

The dissolution of parliament came after Mr Sirisena, the United Freedom Alliance leader, triggered a constitutional crisis earlier this month when he unceremoniously dumped Ranil Wickremesinghe from the prime minister's office.

He named Mahinda Rajapakse as the new leader, but appeared to dissolve parliament and call elections as he had failed to gain enough parliamentary votes to secure backing for the move.

Ousted United National Party (UNP) Prime Minister Ranil Wickremesinghe speaks from his office November 10, 2018 in Colombo, Sri Lanka. credit: Paula Bronstein /Getty Images AsiaPac

Mr Rajapakse’s decade-long term as president was marked by accusations of human rights abuses and brutality but he is popular with nationalists for ending the civil war with the Tamil Tigers.

Both he and Mr Wickremesinghe continue to claim the role of prime minister in a standoff that has paralysed the Sri Lankan government. The deadlock is likely to continue until the January 5 snap elections.

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Ajith Perera, an MP from Mr Wickremesinghe’s UNP said: "We are requesting the election commission to solve this issue peacefully without creating a bloodbath in the country.”

On October 28 a bodyguard working for one of Mr Wickremesinghe's sacked ministers fired live rounds at a mob in Colombo, resulting in one death.

Mr Wickremesinghe’s supporters want the snap elections annulled on legal grounds because they lack parliamentary backing. They believe the election is a ploy by Mr Sirisena to gather more parliamentary support for Mr Rajapaksa.

Several legislators have claimed that they have been offered bribes to join his cause.

Buddhist monks hold a peaceful protest and demand respect for the country;s democracy, on November 6, 2018 in Colombo, Sri Lanka. Hundreds of Buddhist monks gathered in the capital Colombo. credit: Buddhika Weerasinghe /Getty Images AsiaPac

Mangala Samaraweera, Mr Wickremesinghe’s finance minister, said the president had “kicked the constitution in the teeth. We will go to the courts. We will fight in the courts, we will fight in parliament and we will fight at the polls.”

The UNP said: “This dissolution by the President is illegal and goes against the constitution. We will be fighting this to ensure that democracy reigns supreme in the country. He has robbed the people of their rights and the democracy that we have enjoyed.”

Mr Rajapaksa was president of Sri Lanka from 2005 to 2015. Mr Sirisena served as a minister under Mr Rajapaksa before defeating him in 2015 elections after allying himself with Mr Wickremesinghe.

Mr Sirisena, who accused Mr Rajapaksa of dictatorial ambitions, fell out with Mr Wickremesinghe over Indian involvement in Colombo Port.

The US State Department said: “The US is deeply concerned by news the Sri Lanka parliament will be dissolved, further deepening the political crisis.

“As a committed partner of Sri Lanka, we believe democratic institutions and processes need to be respected to ensure stability and prosperity.”