A senior police officer believed to be close to absconding police officer Rao Anwar was detained along with a constable over their alleged involvement in the extrajudicial killing of Naqeebullah Mehsud at an abandoned farmhouse outside Karachi on January 13, it emerged on Monday.

Two senior police officers on condition of anonymity told Dawn that former DSP Malir Qamar Ahmed has been taken into custody as part of the probe into Mehsud's killing.

They said DSP Ahmed had "confessed" that he was present during the ‘encounter’ in Shah Latif Town, while call data records also corroborated the same.

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Another policeman known with his alias Guddu has also been detained, the officers added.

In his statement before the investigation team, constable Guddu "confessed" that he had arranged the sub-machine guns (SMGs) which were allegedly used to kill Mehsud and three other persons in the 'encounter'.

One of the senior officers said call data records of three cell phones used by former Malir SSP Rao Anwar showed that he had contacted other officers on the day of the 'encounter', which also established that DSP Ahmed was present at the scene.

The data also showed that Anwar remained in constant touch with a media person for live coverage of the 'encounter' from the site of the shootout, the officer revealed.

Mehsud, a native of South Waziristan residing in Karachi's Sohrab Goth area, was among the four killed in an 'encounter' days after allegedly being picked up from a tea stall near the area. Following an uproar over social media, Rao Anwar had insisted all four killed were terrorists — a claim refuted by a high-level police inquiry that declared Mehsud innocent.

The demand for the arrest of Mehsud's killers eventually transformed into a movement for rights of citizens of Federally Administered Tribal Areas, with a protest in Islamabad ending with assurances from the prime minister to take up the protesters' demands at relevant forums.