"The jail authorities have received the court verdict for further action," an official, who carried the apex court's verdict wrapped in a red coloured folder, told reporters.
The development came nearly two hours after Chief Justice Surendra Kumar Sinha-led four judges bench signed the full text of the judgment, dismissing Nizami's final review plea.
73-year-old Nizami's final appeal against his death sentence for war crimes committed during the 1971 Liberation War against Pakistan was rejected by the apex court on May 5.
Attorney general Mahbubey Alam said Nizami, the leader of Bangladesh's largest Islamic party, could now be hanged anytime unless he seeks presidential clemency.
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"He will have to be given a reasonable time to take the decision...But if the answer is 'no', the government could hang him anytime," he said.
Jamaat on Saturday, however, said: "question doesn't arise at all to seek mercy to anybody else except Allah".
Nizami's his eldest son and lawyer Najib Momen supplemented the party statement, saying "he (Nizami) will not seek clemency to the President".
Authorities last night shifted Nizami to Central Jail from a suburban prison, signalling his imminent execution.
Meanwhile, elite anti-crime Rapid Action Battalion (RAB) forces overnight joined the police in riot gears to enforce a tight vigil around the Central Jail, where the officials said the noose was ready for him to be hanged.
"I can't tell you when his (Nizami's) death sentence will be executed but I want to say that the verdict will be carried out after exhausting all legal procedures," Home Minister Asaduzzaman Kamal told PTI.
He was given capital punishment in October 2014 by the tribunal after being convicted of "superior responsibility" as the chief of the infamous Al-Badr militia forces in 1971.
He was particularly found guilty of systematic killings of over 450 people alone in his own village.
Nizami appears to be the last remaining top perpetrators of crimes against humanity as Bangladesh so far executed four war criminals since the trial process began six years ago.