The FBI was asked to help investigate a plot to blow up the U.S. Embassy in Uganda, and 20 people are in custody in connection with that case, a government official says.

And in Hamburg, Germany, the U.S. consulate was under increased security for a second day Friday after German police received tips on plans to attack it.Dozens of police and several armored personnel carriers guarded the white, palacelike building, which stands near a tributary of the Alster River.

Uganda's regional cooperation minister Amama Mbabazi told a parliamentary session Thursday that the FBI agents were invited to Uganda after the Aug. 7 bombings of the U.S. embassies in neighboring Kenya and Tanzania in which 259 people, including 12 Americans, died.

"It is true that the Ugandan government, through security services, asked for and obtained services of the FBI for expertise on bomb attacks which are beyond our capacity to handle," Mbabazi said.

He said Ugandan intelligence officials had learned that the group that carried out the bombings in Nairobi and Dar es Salaam also planned to attack the U.S. Embassy in Kampala.

American intelligence officers also helped thwart the plot, The Washington Post and The New York Times reported Friday. Ugandan authorities were aided by information from the CIA.

U.S. installations around the world have tightened security in response to threats since the East Africa bombings.

Friday, a U.S. official in Dushanbe, capital of the Central Asian nation of Tajikistan, said the embassy there may temporarily close because of concerns about terrorism.

Tajikistan is adjacent to Afghanistan, which the United States has accused of harboring Islamic extremist Osama bin Laden.

Among those detained in Uganda are the two alleged ringleaders, arrested last week as they tried to enter the country from Kenya. The two men are believed to be associates of bin Laden, the suspected mastermind in the bombings of U.S. embassies last month, the Post said.

Over the weekend, security officials said 18 people had been arrested in connection with plans to hit American and Ugandan targets in the country. It was not clear when the other two people were detained.

More than a dozen FBI agents worked with the Ugandan Anti-Terrorism Squad to uncover the recent plot, seizing documents from the homes and businesses of the suspects.