Kabul, Nov 18 (DPA) Pakistani President Asif Ali Zardari and US Secretary of State Hillary Rodham Clinton arrived in Kabul Wednesday, a day ahead of the inauguration of President Hamid Karzai for a second term, officials said.

Karzai was declared winner of Afghanistan's fraud-marred election after his main challenger Abdullah Abdullah dropped out of a run-off scheduled for Nov 7.

Clinton was in Afghanistan to take part in the ceremony at the heavily fortified presidential palace Thursday, where Karzai will be sworn in for the second five-year term, the US embassy said in a statement.

'Clinton arrived in Afghanistan today for a brief visit,' the statement said, adding, 'She will meet with President Karzai this evening and attend inaugural events tomorrow.'

This is the first time Clinton is coming to Afghanistan since taking office as secretary of state.

President Zardari also arrived in Kabul Wednesday evening, where he called on Karzai in his palace in downtown Kabul, Karzai's office said in a statement.

Security was stepped up drastically ahead of the event for fears of attacks by Taliban militants. Additional heavily armed security forces were seen patrolling city boulevards while new checkpoints were erected in various parts of the city to inspect vehicles.

Hundreds of foreign dignitaries, including heads of states and foreign ministers, are expected to attend the event.

Karzai, who has become an increasingly unpopular leader because of endemic corruption marring his government in the past five years, is under mounting pressure by Western leaders to reform his cabinet and crack down on widespread graft.

During her week-long Asian tour, Clinton called repeatedly on re-elected Karzai from different Asian capitals to take firm steps to stamp out corruption in his new administration or risk the loss of US civilian aid to his government.

In a sign to show that he is willing to bow to international pressure, Karzai's government unveiled an anti-corruption unit and major crime fighting force Monday. The president has also repeatedly said in recent weeks that no corrupt official would have a place in his future administration.

Clinton's visit also comes at the time when US President Barack Obama is in the final stages of consulting with his security advisers on whether to send additional troops to the strife-torn country. Around 68,000 US troops are already stationed in Afghanistan.