The double-amputee, who claims he mistook his girlfriend for an intruder when he shot her, has remained largely out of public view amid intense international interest in his case.
His spokeswoman, Anneliese Burgess, last week said the 26-year-old athlete had been "very isolated" but had begun a process of "interacting with people".
But South African press reports said Pistorius shocked patrons when he turned up, looking "relaxed and happy", at a party at the popular Kitchen Bar restaurant last Saturday.
Reports quoted people at the restaurant as saying Pistorius, sporting a beard, was flirting with several women and "knocking back" shots, which are known as shooters in South Africa.
"He was drinking shooters and he was flirtatious," one woman told the local Sunday Times.