(CNN) -

South African sprinter Oscar Pistorius was involved in a nightclub dispute over the weekend, after another patron "started to aggressively interrogate him" on matters relating to his murder trial, his spokeswoman says.

Reports of the incident and subsequent tweets by Pistorius -- his first activity on Twitter since the one-year anniversary of his girlfriend's death -- have grabbed headlines in South Africa and around the world.

Pistorius, 27, is accused of murdering his girlfriend Reeva Steenkamp, 29, on Feb. 14, 2013.

The Olympic sprinter admits firing the bullets that killed Steenkamp, but denies murder, saying he mistakenly thought he was defending himself from an intruder.

South African media reported Monday that Pistorius had been involved in an altercation Saturday at the VIP Room in the Sandton area of Johannesburg.

Pistorius' spokeswoman Anneliese Burgess confirmed to CNN Tuesday that her client had been at the venue with one of his cousins, sitting in a VIP section, when he was approached by another patron.

"The individual, according to my client, started to aggressively interrogate him on matters relating to the trial. An argument ensued during which my client asked to be left alone," she said.

"Oscar soon thereafter left the club with his cousin. My client regrets the decision to go to a public space and thereby inviting unwelcome attention."

The day after the incident, Pistorius tweeted a photo montage showing him with children on prosthetics or stumps.

The text accompanying the photos reads, "You have the ability to make a difference in someones life. Sometimes it's the simple things you say or do that can make someone feel better or inspire them."

This was followed by a second tweet, in which the sprinter posted a photographed passage from "Man's Search for Meaning," a book by Holocaust survivor Viktor Frankl.

The text says love is the "ultimate and highest goal" and describes how a man with nothing "may still find bliss ... in the contemplation of his beloved."

"In a position of utter desolation, when a man cannot express himself in positive action, when his only achievement may consist in enduring his sufferings in the right way -- an honorable way -- in such a position man can, through loving contemplation of the image he carries of his beloved, achieve fulfillment," it says.

Pistorius posted a third tweet Monday, a prayer written across a photo of a misty river -- credited to the Christian website crosswalk.com. The text reads: "Lord, today I ask that you bathe those who live in pain in the river of your healing. Amen."

The postings have prompted messages of support, bewilderment and condemnation on the social media site, with some Twitter users questioning why Pistorius had visited a nightclub while on trial.

Pistorius' murder trial has been adjourned until Aug. 7, when closing arguments are scheduled to begin.