COLOMBO: Sri Lanka's parliament will meet on Tuesday after President Gotabaya Rajapaksa dissolved his cabinet and sought to form a unity government to find a way out of the island nation's worst economic crisis in decades and quell public anger.

The country of 22 million people has been suffering from a shortages of food, fuel and prolonged power cuts lasting up to 13 hours, triggered by a lack of foreign exchange that has stalled imports.

Opposition parties and even members of Rajapaksa's ruling alliance rejected the move for a unity government, setting the stage for a test of strength in parliament.

"You could see the composition of parliament changing today," said lawyer Luwie Niranjan Ganeshanathan, who specialises in constitutional issues.

In a wave of unprecedented spontaneous demonstrations across Sri Lanka, including large gatherings in the commercial capital Colombo, protesters have called for Rajapaksa and members of his powerful ruling family to resign. His brother, Mahinda Rajapaksa, is the prime minister.

"A lot of people are finding it difficult to get a square meal. You have to queue up to get gas and milk powder. Queues for everything," said Upali Karunatilake, 54, a school van driver.

"Even small children are saying that Gotabaya (the president) must be removed," Karunatilake said.

Sri Lanka's ruling coalition won 145 out of 225 seats in the last parliamentary election. However, some of its 11 coalition partners that collectively hold 30 seats have indicated they will sit independently in parliament.

"If the government loses its majority, you could see the opposition bringing in a vote of no confidence but there is parliamentary procedure that goes around it first and is unlikely to happen immediately," Ganeshanathan said.

If a vote of no confidence is adopted, then the president can appoint a new prime minister, he said.

Or, if the government loses its majority, the opposition can also table a resolution to dissolve parliament and call for snap elections, Ganeshanathan added.