"Modi ji must answer as the international media like New York Times, Washington Post, London-based Jane Information group, Daily Telegraph, the Guardian and Reuters, are reporting that there is no proof of militant losses at Balakot in Pakistan," PTI quoted Sibal as saying.
"You are guilty of politicising terror," he said on Twitter.
Congress media in-charge Randeep Surjewala also asked the prime minister to clear the doubt as one of his ministers was denying TV news that 300 terrorists were killed in the air strike on Feb 26.
"Modi ji, Your central minister is denying TV news that prime minister Modi has never confirmed the killing of 300 terrorists in IAF air strikes in Pakistan. Is it true. If not, the prime minister should tell the truth to the country," Surjewala said on Twitter and shared images of a news report about Union minister SS Ahluwalia in this regard.
The Indian Air Force had on February 26 conducted a pre-emptive air strike on a JeM terrorist camp in Pakistan's Balakot to avenge the Pulwama attack in which over 40 CRPF personnel were killed.
Earlier in the day, Punjab minister and Congress leader Navjot Singh Sidhu said, "300 terrorist dead, Yes or No? What was the purpose then? Were you uprooting terrorist or trees? Was it an election gimmick? Deceit possesses our land in guise of fighting a foreign enemy. Stop politicising the Army, it is as sacred as the State," he said, adding "Oonchi Dukaan, Pheeka Pakwan" (big talk, no delivery).
He said, "Skimmed milk masquerades as cream, things are seldom as they seem."
He also put out a video of claims made by people in Pakistan about the damage caused by India's air strike.
"Meet such people whose real faces are hidden behind and their false faces are seen," he said, in an apparent dig at the BJP leadership.