In a statement issued here, Khan said Mollah's execution was "very unfortunate and a tragic step". He contended that some circles had declared it a "judicial murder".
"There is no doubt that he was hanged because of his loyalty and solidarity with Pakistan in 1971," he said.
"Till the very end before creation of Bangladesh, he remained a supporter of a united Pakistan and today every Pakistani is saddened and grieved on his death," he added.
Mollah was the first politician to be hanged for crimes committed during Bangladesh's war of independence from Pakistan.
Noting that 42 years had passed since the events of 1971, Khan said it was the demand of international relations that "events of the past should be put behind and a new era should be started".
The execution was an effort to "revive old wounds of the past", he claimed. "It would have been better if the Bangladeshi government had shown farsightedness, large- heartedness and magnanimity instead of opening old wounds," he said.