No-one was injured in the blast on September 4, which was confirmed to RFE/RL by Tashkent police.
It was caused by an explosive device left at a bus stop, said the police, who said they were searching for a suspect witnessed dumping it there before making a getaway.
Only much later in the day, Uzbekistan's Interior Ministry issued a statement saying that the explosion was a security exercise designed to test the capacity of the security forces to react to a terrorist attack.
The explosion took place near Tashkent’s Chorsu Bazaar in the heart of the Old Town, which was the scene of a terrorist attack in 2004. That episode introduced suicide bombing to Central Asia and prefaced a spate of explosions in Tashkent and Bukhara that left at least 19 people dead.
The device blew up near the Tokhtaboy Mosque, one of Uzbekistan’s largest and best-known places of worship, where Obidkhon Qori Nazarov — a religious leader whose preaching displeased the authoritarian regime of President Islam Karimov — was once the imam.
He fled Uzbekistan in 1998, and in 2012 was the subject of an assassination attempt in Sweden, where investigators have pointed the finger at the Uzbekistani authorities for the crime.
The blast — extremely rare in a country with a stifling security force presence — took place one week after Washington asked Uzbekistan to join the US-led international coalition against IS.
The explosion, which was not immediately reported by the tightly controlled state media, also came less than a month after the Islamic Movement of Uzbekistan terrorist group swore allegiance to Islamic State.
The IMU was formed in the 1990s with the aim of overthrowing the Karimov regime and establishing a caliphate in Central Asia, but was driven out of Uzbekistan and based itself on the Afghanistan-Pakistan border as a Taliban ally.
Karimov’s staunchly anti-Islamist administration periodically expresses concern about the threat to Uzbekistan from the IMU and from the IS group, though analysts are divided about the potential threat.
Human rights campaigners accuse Tashkent of talking up the risks to justify persecutions against non-extremist Muslims, thousands of whom languish behind bars for practicing their religion beyond the strict remit allowed by the state, according to a report published by Human Rights Watch last year.
Uzbekistan suffered its most serious terrorist attack in 1999, when over a dozen people were killed in a series of car bombs targeting government buildings in downtown Tashkent.