The Zimbabwe Conservation Task Force has said that, Jericho, the brother of Cecil the lion, has been shot dead by poachers.
The organisation on Facebook said: "It is with huge disgust and sadness that we have just been informed that Jericho, Cecil's brother, has been killed at 4pm today, we are absolutely heartbroken."
However, Brent Stapelkamp, a field researcher for the Hwange Lion Research Project which is monitoring the lion with a GPS tag has disputed the claim.
Stapelkamp said "He looks alive and well to me as far as I can tell,"
Jericho is thought to have been protecting Cecil's cubs.
The hunting of 13-year-old Cecil by US dentist Walter Palmer on 1 July caused global outrage when it was made public earlier this week.
Mr Palmer allegedly paid park guides $50,000 (£32,000) to kill the lion, who was a hugely popular attraction at the Hwange National Park in Zimbabwe.
More than 140,000 people have signed the petition to extradite the Minnesota dentist to Zimbabwe to face justice.
Zimbabwean authorities have now suspended the hunting of lions, leopards and elephants in the area while it investigates the killing of another lion in July.
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