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.