Ashraf Ghani has been inaugurated as Afghanistan's new president and has sworn in Abdullah Abdullah as chief executive.
The two men took their oaths of office in Kabul on September 29 in Afghanistan's first ever democratic transfer of power.
Outgoing president Hamid Karzai had been Afghanistan's only leader since 2001.
"I will abide by the constitution and other laws and protect their implementation," Ghani said in an oath administered by the chief justice.
Ghani was officially declared the winner of the presidential election on September 21, some three months after the second round of the election was conducted.
He has pledged to sign an agreement with the United States to allow about 10,000 American troops to stay in the country after the international combat mission ends on December 31.
Abdullah, as chief executive, will have new role similar to a prime minister, in a government structure far different to Karzai's all-powerful presidency
Afghanistan's democratic transfer of power was plagued by accusations of electoral violations from both Ghani and Abdullah, both of whom claimed to have won the June 14 election.
Under heavy pressure from the US and UN, the two candidates eventually agreed to form a "national unity government", and Ghani was declared president after an audit of nearly eight million ballot papers.
John Podesta, counselor to President Barack Obama, led a 10-strong US delegation, with President Mamnoon Hussain representing Pakistan and Vice President Hamid Ansari travelling from India.
Many other countries, including Britain and France, were represented only by their ambassadors in Kabul, while China sent Yin Weimin, minister of human resources.
In his inaugural speech, Ghani said his priority is to bring peace to the country.
"We ask opponents of the government, specially the Taliban and Hezb-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," he added.
On the eve of the swearing-in, a small bomb hidden in a military vehicle exploded outside the presidential palace complex, injuring the driver.
On inauguration day, two bomb attacks took place on the road connecting the country's main airport with the palace.
One roadside bomb did not result in any deaths or injuries, but a second attack about a kilometer from the airport by a suicide bomber killed at least four civilians, police said.
In early international reaction to the inauguration, Swedish Foreign Minister Carl Bildt tweeted on September 29: "First ever peaceful and democratic transition of power in Afghanistan. Hugely important. And encouraging."
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.
Based on reporting by BBC, Reuters, and AFP