Two sons of former Pakistani prime minister Zulfiqar Ali Bhutto made a public appeal here today that his life be spared and vowed to seek vengence and revolution in Pakistan if he is executed.

"There will be bloody civil war in Pakistan" if Bhutto's death sentence is carried out, said the condemned man's eldest son, Mir Murtaza Bhutto. 24. His brother, Shah Mawas Bhutto. 20. said he would return to Pakistan from exile here "and take my revenge."

Their appearance at a press conference and in interviews on national television news shows here followed the broadcast last night of a televised BBC interview with Pakistani President Mohammed Zia ul-Haq. He defended Bhutto's trial, conviction and death sentence as the just products of orderly Pakistani judicial procedures.

In the face of worldwide criticism of the death sentence and pleas that Bhutto's life be spared, the Pakistani government has published thick "white papers" alleging that Bhutto also had interfered with democratic processes as prime minister, deprived many Pakistani citizens of their civil rights, gagged the press and illegally amassed wealth for himself and his family.

Alluding to those charges in his BBC interview from Pakistan, Zia said that Bhutto's conviction and death sentence show that "no one is above the law in Pakistan."

Zia also lightly dimissed the personal appeals he has received from a number of world leaders, including President Carter and British Prime Minister James Callaghan. Zia said with a smile they amounted to a "trade union appeal" from the world's politicians to save one of their own. Each letter, he said, began with expansive, flowery denials of any intention to interfere with Pakistan's internal affairs, followed by "a big but" and an appeal for clemency for Bhutto that Zia said did constitute such interference.

At their press conference today, staged by a public relations firm in an exclusive London hotel, Bhutto's sons said that Zia, in the BBC interview, "was laying the groundwork to turn down the appeals for clemency."

They said that only "overwhelming security arrangements" and continuing "large-scale arrests" in Pakistan, have thus far prevented a violent reaction.