KABUL, Afghanistan - In a tentative yet risky attempt to exert his authority beyond Kabul, Hamid Karzai summarily fired more than 15 top provincial officials yesterday, accusing them of abuse of authority, corruption and in some cases narcotics trafficking.

The firings are the first large shake-up in the 10 months Karzai has been Afghanistan's president.

If the officials step down as ordered, more dismissals would be likely, his spokesman signaled yesterday. But if the orders are flouted, Karzai would come off as a feeble ruler whose writ ends a few miles from his 19th-century presidential palace.

"There will be a little trouble, of course," Sayed Fazl Akbar, a presidential spokesman, said yesterday while predicting that Karzai would prevail. "Both the nation and the people are behind these decisions.

"This is the strength of the situation."

Karzai's calls for a law-abiding, multiethnic government appear to enjoy wide popular support across Afghanistan, but he has no national army to enforce his orders.

Early opposition in Washington stymied his repeated requests that an international peacekeeping force be expanded beyond Kabul.

Militia leaders still rule large swaths of the country as their personal fiefs, using customs duties, local taxes and in some cases opium trafficking to raise their own armies.

Aid groups have complained that the sway of those leaders has been bolstered by a Pentagon policy of hiring warlords' soldiers to aid U.S. forces in the hunt for the remnants of al-Qaida and the Taliban.

Karzai's dismissals last night appeared to be a first step to undermine the warlords' power. While the moves do not directly challenge the country's most powerful warlords, the presidential decree ordered the disbanding of three military units and the removal of several powerful provincial intelligence chiefs.

They also targeted the city of Jalalabad in eastern Afghanistan, which has re-emerged as a center of the opium trade since the fall of the Taliban. Karzai fired Jalalabad's mayor and the directors of its customs, public works and agriculture departments.

"All these people who were fired, the reason is corruption and not obeying the laws," Akbar said. "Also some of them are caught in drugs trafficking."

The dismissals appeared to be spread across the country's different ethnic groups.

Karzai, a member of the country's largest ethnic group, the Pashtuns, has tried to ease ethnic divisions simmering in the country after a decade of civil conflict following the 1989 Soviet withdrawal.

His riskiest moves yesterday involved firing provincial intelligence chiefs and disbanding military units.

Among the most powerful let go were the heads of intelligence in the cities of Kandahar in southern Afghanistan and Mazar-e Sharif in northern Afghanistan.

An assistant to Kamaluddin Gulalai, the head of intelligence in Kandahar, said in a telephone interview last night that Gulalai had not been informed of his dismissal.