TTP spokesperson Mohammad Khurasani said Sajna was also heading the Mehsud faction of the Taliban and that, following his death, the top leadership appointed Mufti Noor Wali Wali to replace their dead deputy.
Tariq says Wali enjoys the backing of Mullah Fazlullah, the leader of the Pakistani Taliban who is believed to be hiding in Afghanistan.
Helmand is one of Afghanistan's most violent provinces, and also a major source of opium, the narcotic used to make heroin.
Pakistani officials had earlier reported unconfirmed reports about Sajna's killing in a United States strike.
The slain commander was also believed to be closely linked to the Haqqani network blamed for staging high-profile terrorist attacks against local and USA -led forces in Afghanistan.
In December past year, members of the group attacked a college in the Pakistani city of Peshawar, shooting dead at least nine people and injuring 36.
"I have seen some reports on social media about a drone strike, but I have not heard anything from our relevant security agencies", Faisal said.
"We know that a Taliban fighter killed 16 militiamen fighting alongside government forces, but who these forces belong to, we don't know yet", said the spokesman, Omar Zwak.
Relations between the United States and Pakistan have been strained since January 1 when Trump's denounced Pakistani "lies and deceit" over its support for the Afghan Taliban and their allies. Two months in, 2018 has already seen two drone strikes killing at least six "suspected" militants in Pakistan.
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