Australia and the United States have been warned their Indonesian embassies will be bombed if the executions of three Bali bombers go ahead.
The threat, sent by text message to Indonesian police today, sparked a major security operation to ensure the sites were safe. No bombs were found.
Mukhlas, his younger brother Amrozi, and Imam Samudra have warned that others will carry out revenge attacks if they are put to death.
Security forces are on high alert across Indonesia, with the executions expected any day.
The threat reportedly said: "I have put TNT bombs around the US and Australian embassies. I will pull the trigger if Amrozi and his friends are executed".
"We are investigating. We are tracking who sent the SMS, but nothing has been found so far," Indonesian police spokesman Abubakar Nataprawira said.
Australia's Department of Foreign Affairs and Trade said "threats of this nature are not unexpected in the current circumstances".
It said the embassy was in close contact with Indonesian authorities about security issues.
A US embassy spokesman confirmed a threat had been received, and said the embassy was working closely with local police.
Australia lost 88 nationals, and the US seven, on October 12, 2002 when the three bombers targeted nightclubs on the Indonesian resort island of Bali.
A total of 202 people died in the blasts, which the bombers said were revenge for US aggression in Afghanistan and Iraq.
Indonesia has said the trio will be executed in "early November".
Firing squads have been assembled and two helicopters are waiting on Nusakambangan Island in Central Java, where the bombers are jailed, to take their bodies home for burial.
The activity has sparked intense speculation that the executions are imminent. However some observers say they may not happen until after tomorrow - the last day of a five-day visit by Britain's Prince Charles.
Bali governor Made Mangku Pastika, a former police chief who led the investigation into the bombings, said he hoped for the sake of survivors and victims' families that the bombers' deaths would happen soon.
"I hope they may come any time because once we are frightened the terrorists win," he told reporters.
Meanwhile, about 30 angry supporters have arrived at Mukhlas and Amrozi's home village of Tenggulun in East Java.
In emotional speeches at an Islamic boarding school, they denounced the planned executions as "murder".
"There are hundreds of us waiting to come ... If Amrozi is executed a thousand more will come," said Abdulrahim, a member of the group led by radical cleric Abu Bakar Bashir.
Bashir is one of the founders of the Jemaah Islamiah regional terror network, which is blamed for the Bali bombings and other attacks across Southeast Asia.
Other supporters wore balaclavas and gave shouted speeches vowing destruction for the United States, Australia and Israel.
A brother of the condemned men, Jafar Shoddiq, made an emotional appeal for support from Muslims everywhere.
"All Muslims besides those who support us will come without being invited," he said, before shouting: "Raise your voice ... raise your voice to prevent disaster from God." Mujazzin Marzuki, a leader of Bashir's group, said: "We reject the executions, they are murder." The bombers have failed with each of their appeals against the death sentence, including a last-minute petition filed yesterday.
Relatives of the Australians who died expressed mixed emotions today about the executions.
"Nothing ever heals what's happened," said Ray Mavroudis, 33, the cousin of Coogee Dolphins member David Mavroudis, 29, who died in the bombings.
"But it's going to be peace of mind for a lot of the families and their relatives. The day hasn't come quick enough. It's taken a lot longer than what it should have.
Survivor and Coogee Dolphins player Erik de Haart said the judicial process surrounding the bombers had been protracted, and the execution process was no different.
"It's been going on for six years," he said, adding that he and other club members doubted if the executions would ever go ahead.
"I'd like it to happen eventually - but I am a bit sceptical." Georgia Lysaght, 27, who lost her older brother Scott in the bombings, said the executions would not bring relief or closure.
"We're not vengeful and it definitely doesn't bring closure because no matter what happens, it doesn't bring Scott back."
