KABUL: Ashraf Ghani, a one-time US-based academic, was sworn in as new president of Afghanistan on Monday and used his inaugural speech to call for Taliban insurgents to join peace talks after 13 years of war.

The ceremony at the presidential palace in Kabul marked the country's first democratic transfer of power and opened a new era after the rule of Hamid Karzai, president since the Taliban regime was ousted in 2001.

The June presidential election was engulfed in disputes over fraud, but international donors welcomed Monday's inauguration as a key legacy of the costly military and civilian intervention in Afghanistan.

Nato's US-led combat mission will end in three months but the Taliban still pose a serious threat to national stability, having launched several fresh offensives in recent months.

“We ask opponents of the government, specially the Taliban and Hizb-e-Islami (another militant group), to enter political talks,” Ghani said after being sworn in.

“Any problems that they have, they should tell us, we will find a solution.

“We ask every villager to call for peace. We ask Muslim scholars to advise the Taliban, and if they don't listen to their advice, they should cut off any relations."

Karzai also pursued peace talks with the Taliban, but preliminary efforts collapsed last year when a Taliban office that opened in Qatar was styled as an embassy for a government-in-exile.

The security threat in Kabul was underlined by a suicide attack near the airport on Monday in which police said four civilians were killed. The Taliban claimed responsibility.

Both Ghani and his poll rival Abdullah Abdullah claimed to have won the election, plunging Afghanistan into months of crisis that fuelled the insurgency and worsened the country's dire economic outlook.

Under heavy pressure from the US and UN, the two candidates eventually agreed to form a “national unity government”, and Ghani was declared president a week ago after an audit of nearly eight million ballot papers.

Abdullah was sworn in on Monday as “chief executive”, a new role similar to a prime minister, as part of a power-sharing deal that is likely to cause friction between opposing camps within the government.

Abdullah struck a positive tone at the ceremony, saying that “in this critical period of history, as a team, we are committed to a national unity government based on the political deal”.

Karzai says goodbye

“We made a lot of effort to bring about a long-lasting peace, but unfortunately our hopes did not fully materialise, but I should say that peace will surely come,” Karzai said in an emotional farewell speech to the nation late Sunday.

“I will transfer government responsibilities to the elected president tomorrow and will start my new life as a citizen of Afghanistan.

“I will strongly support the new president, the government and the constitution and will be at their service."

Both Ghani and Abdullah are moderate, pro-Western leaders who have vowed to push ahead with the patchy social and infrastructure progress since 2001, but the country still faces a major threat from Taliban militants.

Large-scale insurgent offensives have been launched in several provinces in recent months, with the Afghan army and police struggling to recapture lost ground.

Nato operations have scaled back rapidly and its combat mission will finish at the end of this year.

Only 33 Nato bases are still active, down from a peak of 800 — leaving local security forces to battle the Taliban with less and less help.

Monday's inauguration opened the way for the new government to sign an agreement allowing 12,500 US-led troops to remain into 2015 on a mission to support and train the police and army.

Ghani promised immediately to reverse Karzai's decision not to sign the deal, and the document is due to be inked on Tuesday.

“The political transition was a success and all those who predicted it was not possible were proven wrong,” Ghani said last week.

“We are one people, one country, and there should not be any doubts in our national unity."

Final results revealed Ghani beat Abdullah 55 to 45 per cent in the run-off vote, though the UN said the election had been affected “significant fraud”.

Karzai, who ruled since the fall of the Taliban in 2001, was constitutionally barred from running for a third term in office.