Mr Rahman was the father of current Prime Minister Sheikh Hasina
Five ex-army officers in Bangladesh have lost an appeal against their convictions for the murder of the country's independence leader in 1975.
The men, who had been convicted of killing Sheikh Mujibur Rahman, the father of current Prime Minister Sheikh Hasina, now face the death penalty.
Correspondents say the focus is now on finding six others accused over the killings who are living abroad.
The trial began more than a decade ago and this was the killers' final appeal.
State lawyer Anisul Haq said the nation "has got justice" after the five-member jury dismissed the appeal.
"We had to travel a long way to come to this."
On hearing the verdict, Sheikh Hasina expressed her gratitude and called on the nation to remain calm. Her spokesman said she had wept when she heard the news the appeal had failed.
The historical background to the Bangladeshi presidential murder
Mr Rahman was killed in 1975, just four years after leading Bangladesh to independence from Pakistan.
The killers also murdered the president's wife, three sons, two daughters-in-law and approximately 20 other relatives and aides as part of a military coup.
Sheikh Hasina, who was re-elected prime minister last December, escaped the massacre only because she was out of the country at the time.
SHEIKH MUJIBUR KILLING
March 1971: Sheikh Mujibur announces breakaway from East Pakistan and establishment of Bangladesh
August 1975: Sheikh Mujibur is killed in a coup
November 1998: Dhaka court orders execution of 15 for his killing. Three later acquitted
Oct 2001: Trial halts after Khaleda Zia elected PM
August 2007: Sheikh Mujibur's murder case resumes
November 2009: Supreme Court rejects appeals against five ex-army officers accused of killing
The five men, who are in prison in the capital, Dhaka, did not deny their role in the death of Mr Rahman, but had said they should be tried in a military rather than a civilian court.
The BBC's Mark Dummett in Dhaka says unless the president pardons them, they could be hanged within the month.
Before the verdict, 12,000 extra policemen were deployed in Bangladesh, with many guarding strategic buildings, including the Supreme Court where the verdict was given.
Our correspondent says there are people who sympathised with what the five on trial were trying to do.
The authorities feared the men's supporters would disrupt the proceedings, although this ended up not being the case, he says.
The government has already blamed supporters of the five men for a grenade attack on one of the prosecution lawyers last month, which left several people injured.
The police arrested a group of their relatives, and the army said it was investigating possible links to serving officers. Nobody has been charged yet for the attack, and those arrested say they had nothing to do with it.
Six fellow plotters, on the run abroad, have also been sentenced to death. A seventh man also found guilty in absentia is thought to have died abroad.
The government the majors helped install passed a law indemnifying their actions and until 1998 they were free men.
But by then Sheikh Hasina had herself become prime minister and the accused were put on trial, found guilty and sentenced to death.
She lost the following elections, and the next government, led by the party which ultimately benefitted from the coup, slowed the process down.
But Sheikh Hasina returned to power earlier this year, and made the conclusion of the trial one of her top priorities.
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