Breaking down in tears, Nasir Dar said he felt like the victims were his family, British media reports said.
Dar blasted his 27-year-old nephew, Khuram Butt, over his involvement in the sickening terror attack and said he could not understand why he slaughtered seven innocent people.
DenouncingButt's extremist ideologies, Dar said: "No religion of the world allows to do this shameful, brutal action."
Butt was one of three terrorists who drove a van through pedestrians on London Bridge before getting out of the vehicle and launching a knife attack in Borough Market on Saturday.
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He said: "When he came he was wearing shalwar kameez (a traditional outfit), he started offering prayers. (He was) very punctual in prayers and he had a beard also.
"Before that these symptoms were not found in him."
Butt was gunned down by police just minutes into the massacre on Saturday night, withthe bodies of fellow jihadis Rachid Redouane and Youssef Zaghbaalso seen dead on the pavement after being hit with a hail of bullets.
Officers in plain clothes - believed to be from Pakistan's Inter Service Intelligence agency (ISI) - have already raided Khuram Butt's family restaurant in Pakistan.
Jhelum lies in a part of Pakistan where many members of the British-Pakistani community originally hail from. The nearby city of Mirpur, in Pakistan-occupied Kashmir, is known as "Little England" due to its large British-Pakistani community.
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