Four candidates remain in Somalia's presidential election, after parliament cast ballots in a first-round vote Monday.

Incumbent President Sharif Sheikh Ahmed led the pack, followed by PDP party leader Hassan Sheikh Mahamud, incumbent Prime Minister Abdiweli Mohamed Ali and Abdulkadir Osoble Ali, a businessman and U.S. citizen.

Parliament was due to go straight into the second-round vote.

The election reflects a final step in a United Nations-backed plan to create a more effective government in Somalia after two decades of chaos.

None of the original 22 candidates won the two-thirds majority required to be selected president in the first round.

If no one receives two-thirds in the second round, the top two contenders will move to a third round where a simple majority is needed to win.

Somalia's recently appointed 262 lawmakers are casting their secret ballots in the capital, Mogadishu.

The United Nations has described the election as “historic.” But critics say it will do little more than reshuffle key figures and positions.

Somalia has not had an stable central government since 1991.

A U.N.-backed transitional government came to an end last month, eight years after it was created. The government never asserted authority, mainly because of infighting and Somalia's chronic violence.