A major terror trial has opened in Astana, hearing allegations that a group of radicals intended to blow the city’s landmark pyramid sky high and plotted to assassinate senior officials, Tengri News reports.

The iconic pyramid, called the Palace of Peace and Reconciliation and designed by British architect Norman Foster, has become a symbol of President Nursultan Nazarbayev’s glitzy capital. It is also a symbol of religious tolerance, every few years hosting a Congress of World and Traditional Religions to promote inter-faith dialogue.

Prosecutor Malika Shashdauletova alleged that the group also planned to attack the HQ of the National Security Committee’s domestic intelligence service (KNB) and murder agents; plotted the assassinations of unidentified “senior figures of the Republic of Kazakhstan”; and planned an act of terrorism at the opening of Astana Opera, the city’s new opera house.

It was not clear if she was referring to the first, ceremonial opening last December, attended by Nazarbayev, or to the opera’s upcoming opening for performances next month.

Shashdauletova said that alleged ringleader Serik Koshalakov opened a kebab shop near an Astana mosque to recruit followers to pursue the ultimate goal of setting up an Islamic caliphate in Kazakhstan.

Media reports did not say whether the six suspects had entered pleas. The judge banned journalists from the courtroom after the first morning, and the trial will be closed.

Terrorism is currently a sensitive topic for Kazakhstan, with two Kazakhstani students charged in the United States this month with obstructing justice in the case of the suspected Boston Marathon bombers, with whom they were acquainted.

Kazakhstan experienced a spate of terrorist attacks after suffering its first suicide bombing in 2011, and has since launched a crackdown on suspected radicals that has seen dozens jailed in closed terror trials.

While most observers acknowledge that Kazakhstan faces a problem with rising radicalism, critics wonder whether the security services’ heavy-handed tactics might not be doing more to fuel extremism than suppress it. Others have suggested that the security services have an interest in exaggerating the threat from alleged extremists they have arrested to make themselves look more effective.

With the evidence heard behind closed doors, there is no way of independently judging whether the six suspects really had the intention or means of carrying out attacks.