Bilal Sofi (17), a resident of Khanyar locality in downtown Srinagar, was was pursuing graduation from Greater Noida's Sharda University.
"If this is genuine (social media post about Sofi joining militant ranks), it's hugely worrying. Sometimes seemingly small actions have huge consequences (sic)," Abdullah wrote on Twitter.
Sofi went missing on October 28 after he left the varsity with official permission to go to Delhi, days after he was mistakenly roughed up during a scuffle between Indian and Afghan students in the campus.
A missing complaint was registered in the case at the Knowledge Park police station in Greater Noida as well as at the Khanyar police station in Srinagar, officials said.
The pictures on social media showed Sofi dressed in a black outfit and claimed he had joined militant group ISJK, an outfit influenced by ISIS ideology.
"If what happened to him at #ShardaUniversity has lead him to choose such a destructive path it's even more tragic. One more life on the path to ruin & one more family in turmoil (sic)," Abdullah tweeted.