Sri Lanka's newly-elected President Ranil Wickremesinghe is likely to expand his Cabinet to accommodate all Opposition parties in the government, according to a senior minister.

Wickremesinghe on Friday appointed an 18-member Cabinet that included Prime Minister Dinesh Gunawardena.

The President is likely to expand the Cabinet to make it representative of all parties in Parliament, Tourism Minister Harin Fernando said, echoing Wickremesinghe's thoughts to local media after taking the oath on Friday.

However, he did not give any timeframe.

The government sources said the new stopgap President would be taking action to accommodate all Opposition parties in government.

Sri Lankan MPs on Thursday elected Wickremesinghe as the country's new president, with the majority of the vote coming from lawmakers representing ousted President Gotabaya Rajapaksa's Sri Lanka Podujana Peramuna (SLPP) party.

There were only two non-SLPP lawmakers in the Cabinet appointed on Friday. Constitutionally, the Cabinet can be extended up to 30 members.

Meanwhile, the main Opposition Samagi Jana Balawegaya SJB has demanded Gunawardena summon Parliament on July 25 to discuss what they alleged was the state violence unleashed on the protesters.

Sri Lankan troops and police armed with assault rifles and batons on Friday forcibly removed anti-government protesters camped outside the presidential office here in a pre-dawn raid.

Police have described the pre-dawn raid on the main camp of the anti-government protesters as a "special operation to take [back] control of the presidential secretariat".

The protesters had vacated the President and Prime Minister's residences and the Prime Minister's office after capturing them on July 9, but they were still occupying some rooms of the President's secretariat.

They also refused to accept Wickremesinghe as the new president, holding him partly responsible for the country's unprecedented economic and political crisis.

The main protest group which blocked entry to the President's Office since April 9, said they would continue their struggle till Wickremesinghe resigned.

Parliament is next scheduled to meet on July 27. Wickremesinghe had already conveyed his wish to prorogue Parliament to have a ceremonial start of the next session.

The government came under intense heat from the international community for attacking the protesters.

Ambassadors of several nations based in Colombo and international rights groups have condemned the attack on protesters.

Wickremesinghe on Friday briefed the Ambassadors and said that the action was limited to moving out a group of illegal occupants from the president's office after due notice to protesters.

The police in a statement said that a senior police official had asked the protesters to vacate the building twice, on July 14 and July 18, but they defied the order and ridiculed the police officers by publicly humiliating them.

Some protesters were seen on Saturday morning at a protest site.

Sri Lanka has seen months of mass unrest over an economic crisis and many blame the former government led by ousted president Gotabaya Rajapaksa and his family for mishandling the island nation's economy.

Protesters also set Wickremesinghe's personal residence on fire and occupied his office during protests last week.

Sri Lanka, a country of 22 million people, is under the grip of an unprecedented economic turmoil, the worst in seven decades, leaving millions struggling to buy food, medicine, fuel and other essentials. Sri Lanka's total foreign debt stands at USD 51 billion.