Sri Lankan President Maithripala Sirisena suspended Parliament Saturday after sacking Prime Minister Ranil Wickremesinghe a day earlier on Friday.
After sacking Wickremesinghe, Sirisena installed former strongman president Mahinda Rajapaksa as prime minister.
Wickremesinghe called the move "unconstitutional", and vowed to prove his majority in Parliament.
Wickremesinghe wrote to the speaker earlier on Saturday demanding he hold an emergency session of Parliament so that he (Wickremesinghe) could prove his majority on the floor of the house.
AFP quoted Parliamentary officials as saying the president had suspended all meetings of the 225-member house until November 16.
The parliament had been due to meet again on November 5 to unveil the 2019 annual budget.
The suspension could destabilise government finances at a time when the country faces an economic crisis.
In a statement, Parliamentary Speaker Karu Jayasuriya called for calm and restraint and for the crisis to be resolved quickly.
European diplomats in Colombo said they were closely following developments and urged both sides to act in line with the constitution, echoing comments made by the United States.
"The ambassador of the European Union as well as the ambassadors of France, Germany, Italy, the Netherlands, Romania and the UK High Commissioner ... urge all parties to fully act in accordance with Sri Lanka’s constitution," they said.
They also urged the rivals to refrain from violence and respect media freedom.