Senior fellow of the Observer Research Foundation, Sushant Sareen, on Saturday expressed regret for using abusive language on Twitter while responding to a tweet put up by writer and activist Gurmehar Kaur in the aftermath of the Pulwama terror attack.

Sareen, a Pakistan analyst at the foundation, deleted his original tweet after the think tank asked him to issue an apology. “The offending tweet has been deleted,” said Sareen. “I regret my choice of words and should have been more careful in responding/reacting. Although I did not personally target anyone and made a generic comment on a phenomenon, it was apt to be misinterpreted, which I regret.”

The think tank said it “maintains highest standards of conduct including in communication, doesn’t support or condone abusive, intimidatory or hateful language in any form”. The foundation also tagged Raji Pillai, who heads its nuclear and space policy initiative and is a member of its Internal Complaints Committee, in its tweet.

Observer Research Foundation’s response came within minutes of Sareen’s tweet sparking outrage online. A number of Twitter users called on the think tank to sack the analyst.

“To all those who are posting angry long messages about how revenge is the only answer,” Gurmehar Kaur had tweeted on Friday. “Honestly I understand the anger. We feel it too. But think – the surgical strikes was an reply to another such cowardly attack and we were all told that this was justice. We proved them weak.” She had also warned against a violent reprisal, saying it “doesn’t do anyone justice”.

In response, Sareen wrote: “I guess sex slavery in a jihadi camp is the new millenial fantasy, a thing these brainless idiots crave for.”