Can my employer cut my salary in half without notice?

I work at an IT company in Bengaluru, and they've suddenly cut my salary by 50% this month without any prior warning or discussion. I am in shock because I have not received any official communication regarding this decision. I rely on this income to support my family, and such a drastic reduction is very stressful. Is this action legal? What are my rights, and how should I address this with my employer?