Asif Ali Zardari was sworn in as the President of Pakistan in Islamabad on Tuesday, after he swept to victory in polls on Saturday.
Zardari, husband of slain former prime minister Benazir Bhutto, was administered the oath of office in English by Chief Justice of Pakistan Abdul Hamid Dogar.
Zardari elected as Pakistan president
Former Prime Minister Nawaz Sharif, who withdrew support to the Pakistan People's Party-led coalition government, was not present at the ceremony.
Karzai attended the ceremony at the invitation of Zardari and sat a few seat away from the Bhutto family members.
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Also present in the audience were leaders of parties in the PPP-led coalition, including Jamiat Ulema-e-Islam chief Maulana Fazlur Rehman, Awami National Party president Asfandyar Wali Khan and Muttahida Qaumi Movement parliamentarian Farooq Sattar, and chief ministers and governors of the four provinces.
The opposition PML-N was represented by its president and Punjab Chief Minister Shahbaz Sharif.
Former President Pervez Musharraf, who resigned in August to avoid impeachment by the PPP-led coalition, did not attend the ceremony. It was not immediately known if he was invited to the ceremony.
Zardari, who swept last week's presidential poll by bagging almost 70 per cent of the votes, on Monday moved into the presidential palace in the heart of the federal capital with his daughters and close aides.
Shortly after Musharraf resigned last month, Zardari had shifted from his private residence to the Prime Minister's House due to security concerns.
After taking oath, Zardari was presented a guard of honour by a tri-services contingent. He also met people from all sections of society.
Zardari would present his vision to take Pakistan forward and a strategy to counter terrorism during a news conference later in the day.