President Islam Karimov (search) blamed suicide bombings against the U.S. and Israeli embassies on the same group behind unprecedented similar attacks earlier this year, pleading in a nationwide TV address Saturday for Uzbeks to spurn extremist Islamic influences.

He spoke after a police officer guarding the U.S. Embassy died overnight from injuries in Friday's attacks, which also hit the chief prosecutor's office in the Uzbek capital, said general prosecutor's spokeswoman Svetlana Artikova (search). That raised the death toll to at least six, including the three bombers.

While not naming the group behind the attacks, Karimov pointedly mentioned Hizb ut-Tahrir, a secretive extremist Islamic group that has spread across Central Asia since the Soviet collapse. The group, whose Arabic name means Party of Liberation (search), claims to disavow violence in its quest to create worldwide Islamic government.

In a bid to crush extremism, Karimov's authoritarian regime has arrested thousands of members of Hizb ut-Tahrir and other Muslims who worship outside state-run mosques, but critics say the campaign has backfired and it has drawn strong international criticism.

"Some international human rights organizations who take Hizb ut-Tahrir under their wing and protect them say they are innocent lambs," Karimov said in the speech late Saturday. "But if this group wanted to create a caliphate (Islamic state) and overthrow the government, how can they do it peacefully, without bloodshed?"

The near-simultaneous triple suicide attacks were the second attacks to hit Uzbekistan this year, raising fears of instability in Central Asia's most populous nation, and took place during the first trial of 15 suspects in the wave of March-April violence that left at least 47 dead.

Karimov said both attacks were organized "from the same group, and serve the same aims," which he said were to sow fear and disrupt the country's "peaceful and stable life."

A source close to Uzbek extremist groups told The Associated Press on Saturday that al-Qaida directed and financed the group behind Friday's bombings and that the attacks were retaliation for Uzbekistan's support of the U.S.-led war on terrorism.

The source, speaking on condition of anonymity, said the group was based in Pakistan and had been founded by several former fighters of the Islamic Movement of Uzbekistan, an al-Qaida-linked terror group, after they fell out with that movement's leaders.

The account squares with testimony of the 15 suspects who went on trial this week for the spring attacks. Authorities said earlier the new extremist group was linked to international terror groups and its members were trained in Pakistan by al-Qaida instructors.

Although the group uses the name Jamoat, or "Society" for its cells, the source said it had no real name.

The source said al-Qaida had targeted Uzbekistan because of its support of the U.S. anti-terror coalition in neighboring Afghanistan. U.S. troops have been based in the southern city of Khanabad since October 2001.

"It's about politics, not religion," the source said, predicting further attacks. "It will calm down here when the U.S. base goes."

U.S. Army Lt. Col. Neal Kemp, commander at Khanabad, told AP on Saturday that he knew of no specific threats against the base but that officials were "taking appropriate steps" after the latest violence.