The bombers said they were keen to be "martyrs"
Three Indonesian Islamic militants condemned to death for the 2002 Bali bombings that killed 202 people have been executed by firing squad.
Imam Samudra, Amrozi Nurhasyim and Ali Ghufron (Mukhlas) were shot at the island prison of Nusakambangan at 0015 (1715 GMT on Saturday), officials said.
They were found guilty of planning twin attacks on nightclubs at the resort of Kuta, popular with Western tourists.
Security forces are on alert across the country amid fears of reprisal attacks.
Members of radical groups have gathered to show their respect in the men's villages, where their bodies will taken by helicopter to be buried.
The BBC's Lucy Williamson, in Cilacap, near the prison, says the execution took place in the darkness surrounded by forest and a handful of witnesses.
Later, a spokesman for the attorney-general's office confirmed that the three men had been shot.
"The autopsy results show that all three are dead," Jasman Panjaitan told a news conference.
"The family members are now bathing the bodies," he added.
Haji Chozin confirmed that his brothers, Amrozi and Mukhlas, had died.
The deaths will not evoke much sympathy in Indonesia, where most people supported the sentence and believed the executions should have been carried out much sooner, our correspondent says.
Supporters of the bombers have been gathering in their home villages
Officials had said the three would be shot in early November but no date had been announced in advance.
The men had apparently requested no autopsy and they had asked not to be buried in state shrouds, but in material brought specially from their family homes.
Since they were sentenced the bombers made several appeals for leniency, and also filed an unsuccessful appeal to be executed by beheading rather that face a firing squad.
They said beheading was a more humane and Islamic form of execution and that being shot amounted to torture.
However, they also said they were keen to be "martyrs" for their dream of creating a South-east Asian caliphate.
The bombings were blamed on the militant group Jemaah Islamiah, widely regarded as a regional affiliate of the al-Qaeda network, but several key suspects have never been caught.
Malaysian Azahari Husin, alleged to be Jemaah Islamiah's top bomb-making expert and to have helped assemble the Bali bombs, was killed by police in eastern Indonesian in November 2005.
Alleged bomb-maker Noordin Mohammad Top and electronics expert Dulmatin, an Indonesian, are still at large.
None of the executed men had ever expressed remorse for the attacks, only saying they regretted that Muslims had been killed.
The two explosions killed 202 people, mostly foreign tourists
A last-minute appeal by relatives of the bombers was rejected by a Supreme Court judge earlier this week.
Some of the victims' families, however, had said they opposed the execution.
Susannah Miller, whose brother was killed, said the deaths would be a "state-sponsored route to martyrdom" which would encourage extremists.
Speaking after the executions, Australian Foreign Minister Stephen Smith said it was "not a day that fills us with any joy or with any celebration".
There were 88 Australians among those who died in the bombings, as well as 38 Indonesians and 28 Britons.
"My first thoughts are for the families of the victims of both the Bali bombings, it's just in my view a terrible reminder of a terrible, horrible event that occurred to family members," Mr Smith said.
Correspondents say that while executing the men has sent a strong message, it could also put the country's hard-won security at risk if it inspires other extremists to carry out similar acts.