President Barack Obama paid a surprise visit to Afghanistan yesterday, his first as US commander-in-chief, to assess his surge of 30,000 troops, designed to end the bloody eight-year war on the Taliban.

The trip, shrouded in secrecy until his arrival amid security concerns, opened with talks with President Hamid Karzai at his Kabul palace, which Mr Obama used to press for a stepped-up fight against corruption and the drugs trade.

"The American people are encouraged by the progress that has been made," Mr Obama told Mr Karzai after the one-on-one meeting, which included an invitation for the Afghan leader to visit Washington on May 12.

But Mr Obama also pressed Mr Karzai, with whom he has had a testy relationship, to "continue to make progress" on the civilian front, including on good governance, the fight against corruption and the rule of law.

He also said he had made the dramatic through-the-night flight to Afghanistan to thank US troops for their "incredible efforts" and their "tremendous sacrifices" a long way from home.

Mr Karzai thanked American taxpayers for helping "the rebuilding and re-establishing" of Afghanistan civilian institutions and government.

Mr Obama landed in Afghanistan amid a spike in deaths of foreign troops in the escalating war, and as the first big offensive of his new strategy unfolds in Helmand province, with Taliban strongholds in Kandahar among future targets.

His secret journey began when he left his Camp David retreat outside Washington and boarded Air Force One at Andrews air force base for a non-stop flight to the Bagram military base outside Kabul.

After touching down after dusk, Mr Obama flew by helicopter to the palace with key aides, including Rahm Emanuel, his chief of staff and political adviser David Axelrod.

The visit, expected to last only a few hours in the unstable Afghan capital, was also scheduled to include in-person briefings for Mr Obama by war commander General Stanley McChrystal and US ambassador to Kabul Karl Eikenberry.

Mr Obama and Mr Karzai met almost immediately after he touched down, and emerged from the palace on a red carpet for a welcoming ceremony, including an Afghan guard of honour and the US and Afghan national anthems.

Private, and likely candid talks between the two leaders were followed by an expanded session with the Afghan Cabinet and a shared meal.

Mr Obama landed in Afghanistan emboldened by the best week of his presidency, after passing a historic health care reform law and concluding a major nuclear arms control treaty with Russia.