LA PAZ, Bolivia (AP) _ U.S. drug czar Bob Martinez met President Jaime Paz Zamora on Thursday despite bomb threats that prompted police to lay on heavy security.

Police reported a series of threats Wednesday, the day Martinez arrived. Unexploded bombs were recently found at the U.S. Consulate and other buildings. Martinez, director of the U.S. Office of National Drug Control Policy, is visiting Mexico, Colombia, Peru, Bolivia and Panama with the aim of ''personally finding out the challenges that are being faced in the hemisphere with regard to the anti-drug fight,'' the U.S. Embassy said.

U.S. officials are upset by reports of corruption among drug enforcement officials in the government. On Monday, one of the country's top smugglers, Carmelo Dominguez, fled a La Paz jail, allegedly with the assistance of the warden. Dominguez was recaptured Tuesday and the warden detained.

U.S. Ambassador Robert Gelbard called Dominguez' escape a ''blatant act of corruption involving one of the most important drug smugglers in Latin America.''

In another statement before Martinez' arrival, Gelbard said: ''The U.S. govermment is seriously concerned with the precipitous drop in performance across the board in anti-drug operations.''

But Paz Zamora told Martinez that ''to my view the relations between the U.S. and Bolivia have reached their highest level ... never before have Bolivia and the U.S. had such basic agreement on many issues.''

Martinez will remain in Bolivia until Saturday and is holding meetings with members of Paz Zamora's Cabinet and U.S. Embassy and anti-drug officials.

On Friday he is scheduled to tour the Chapare, Bolivia's coca leaf producing region, site of a U.S.-financed training camp for Bolivian narcotics police.

Washington temporarily suspended economic aid to Bolivia this year after the interior minister named Col. Faustino Rico Toro, a former high-ranking officer in a cocaine-backed military government, as chief of Bolivian anti- drug efforts.

The interior minister and the national police chief subsequently resigned and Rico Toro never took up the appointment. Bolivia is overhauling its anti- drug forces and removed several officers for incompetence or corruption.

The government permits the presence of 44 U.S. Special Forces personnel to train two Bolivian army battalions in anti-drug operations. The military trainers are based near Santa Cruz, 350 miles east of La Paz. Farmers and workers held protest marches over the U.S. military presence.

Washington is providing $44.6 million in military aid to Bolivia to be used for anti-drug operations.

Coca leaf farmers destroyed nearly 20,000 acres of coca plants last year. They receive $2,000 for every 2 1/2 acres destroyed.

But coca eradication last month dropped to about 450 acres. The average last year was 1,750 acres s a month.

Bolivia is the world's second largest producer of cocaine, after Colombia. At least 300,000 people in the impoverished nation of 7 million depend on coca leaf cultivation and cocaine production for their livelihood.