Authorities arrested six people Wednesday in connection with the homicide bombings (searchof two Istanbul (search) synagogues as opposition leaders accused Turkey's government of being too lenient toward Muslim radicals.

The suspects include relatives of two suspected accomplices in the bombings, the Anatolia news agency said. A Turkish court charged five with "attempting to overthrow the constitutional structure," which carries a sentence of life imprisonment. A sixth person was charged with "helping illegal organizations," punishable by five years in prison, Anatolia said.

No trial date has been set.

Two attackers, both Turks, blew up pickup trucks outside the synagogues on Saturday, killing 23 people and the two bombers. Foreign Minister Abdullah Gul said the two had visited Afghanistan in the past and that investigators were looking for any Al Qaeda (searchlinks.

An Al Qaeda link would make Turkey, a predominantly Muslim but secular member nation of NATO, a new front in the U.S.-led war on terror.

The role of local militants could mean trouble for the government of Prime Minister Recep Tayyip Erdogan, which has its roots in an pro-Islamic party.

Opposition leaders criticized his government for backing off a countrywide crackdown on militant Islamic groups after coming to power a year ago, and even releasing hundreds of Islamic militants from prison under a four-month-old amnesty.

About 130 Islamic militants who belonged to the Hezbollah, which is not linked to the Lebanon-based group with the same name, have been released in southeastern Turkey under the amnesty, a judiciary official said Wednesday. Scores of others were expected to be released, too.

"There is a risk that potential terrorists may be brought back with this amnesty," Mehmet Agar, leader of conservative True Path Party and former interior minister, said Wednesday. "We should never loosen our fight against terrorism, otherwise the cost would be very high."

Istanbul Gov. Muammer Guler identified the homicide bombers as Mesut Cabuk, 29, and Gokhan Elaltuntas, 22, both from the southeastern town of Bingol.

The town is a hotbed of the underground Islamic group Hezbollah, which is not linked to the Lebanon-based group with the same name. It was not clear if the two attackers had ties to the group.

The daily newspaper Hurriyet, citing police, said Wednesday that the suspects were members of Beyyiat el-Imam, a little-known group formed in Al Qaeda camps in Afghanistan. The group's name is Arabic for "Allegiance to the Imam," or cleric.

Al Qaeda claimed responsibility for the bombings Sunday in messages to two Arabic-language newspapers, but it was not possible to authenticate those claims. An outlawed Turkish radical group called the Islamic Great Eastern Raiders' Front, or IBDA-C, also claimed responsibility, but Turkish authorities said the attack was too sophisticated to be carried out by that group.

Turkey's Foreign Minister Abdullah Gul, speaking in Stockholm, Sweden, said the homicide bombers had traveled to Afghanistan, but cautioned that more investigation was needed to prove they were linked to Al Qaeda.

"I think that we need some more time to better shed light on this issue," Gul said.

Hurriyet identified the homicide bombers' accomplices as 27-year-old Azad Ekinci, a schoolmate of Cabuk, and Feridun Ugurlu. Ekinci and Ugurlu traveled to Dubai in the United Arab Emirates on Oct. 28 before the bombings, Hurriyet said.

Senior United Arab Emirates officials, speaking on condition of anonymity, said Wednesday that one of the men was a resident in Dubai and was working in the country. They said he was not thought to be linked to the bombing. They did not know the whereabouts of the other man.