Moderate Islamist Sheikh Sharif Ahmed was first to be sworn in
Somalia's parliament has sworn in new opposition members as it prepares to elect a new president.
The new members belong to the Alliance for the Re-Liberation of Somalia (ARS), a major opposition group.
Parliament, meeting in neighbouring Djibouti, also extended the mandate of the transitional federal government for another two years.
But the powerful Islamist al-Shabab militia says it will not recognise the new administration.
One-hundred-and-forty-nine ARS members were sworn in, including the group's leader Sheikh Sharif Ahmed who is standing for president.
He was first to take the oath. With his hand on the Koran, he swore to protect Somalia's constitution.
'Fruits of reconciliation'
The expanded administration is part of a United Nations-backed reconciliation process aimed at restoring stability to Somalia after nearly two decades of conflict.
UN special envoy Ahmedou Ould-Abdallah said: "We are going to tell the Somalis to assume their responsibilities. I expect Somalia to form its government and return to the capital Mogadishu."
A number of people have announced their candidacy for the presidency, including Prime Minister Nur Hassan Hussein, former Prime Minister Ali Mohamed Ghedi, and former warlord Mohamed Qanyare Afrah.
Mr Hussein, who is considered one of the front-runners, appealed to groups opposed to the peace process to take part.
"I hope these people will join and see the fruits of reconciliation," he said.
But analysts say it is unlikely that peace will return soon to Somalia.
Al-Shabab has seized the town of Baidoa, which had been the seat of the Somali parliament.
The Islamist militia has declared Sharia law in the town, and parliament now works from Djibouti.
Some 16,000 civilians have been killed in the conflict and a million more have been forced from their homes.
The Horn of Africa country has not had an effective central government since 1991.