KABUL, Afghanistan - Afghans on Monday watched the country's first transition of power since Hamid Karzai became president shortly after the 2001 US-led invasion, as a ceremony opened to inaugurate incoming President Ashraf Ghani Ahmadzai following a long and contentious election campaign.

Ghani Ahmadzai entered the presidential palace wearing a dark black turban popular in the country's south. His electoral challenger, Abdullah Abdullah, who is slated to fill the newly created position of chief executive, sat two seats away, with Karzai anchoring the spot in between.

Karzai - the only president Afghans and the West has known since the invasion - wore a wide smile as he greeted his presidential guards upon entering the palace. Karzai has said he is glad to be stepping down after more than a decade of what the US ambassador recently said was one of the most difficult jobs in the world.

The inauguration caps a nearly six-month election season that began when ballots were first cast in April. A runoff election in June between Ghani Ahmadzai and Abdullah stretched on for weeks as both sides leveled charges of fraud. The United Nations helped carry out what it said was the most thorough recount in its history, a count that reduced Ghani Ahmadzai's vote percentage from 56 percent to 55 percent, but still gave him the win.

But the real power struggle was taking place in marathon talks between the two sides. The political deal the sides agreed to created the new position of chief executive that Abdullah will now fill.

US officials have said they expect Ghani Ahmadzai to sign a security agreement with the US shortly after his inauguration to allow about 10,000 American troops to stay in the country after the international combat mission ends on Dec 31.

Meanwhile, violence continued Monday in Afghanistan. In the eastern province of Paktia, Capt. Mohammed Hekhlas said that a car bomb exploded near a government compound as gunmen attacked, sparking a gun battle that killed seven Taliban militants. Another police official, who gave his name as Azimullah, said four police officers and two civilians also were killed.

In Kabul, where the city is readying for the presidential inauguration, a roadside bomb exploded on the airport road. Officials said no one was hurt or killed.