Can a landlord increase rent before the agreement expires?
Generally no — the rent agreed in a running agreement holds until it ends, unless the agreement itself sets out an increase.
While a rent agreement is running, the rent in it is what applies. A landlord cannot raise it partway through simply because market rates have moved. The agreement is a contract, and the rent is one of its terms.
The common exception is an escalation clause. Many Indian rent agreements say something like "rent increases by 5% on renewal" or "by 10% every 11 months". If that clause is in the agreement both parties signed, the increase is already agreed and takes effect as written — check your own copy before assuming an increase is invalid.
At the end of the term, the landlord is free to propose a new rent, and the tenant is free to decline and move out. Several states that have adopted the Model Tenancy Act framework also require advance written notice of a revision. If you are facing a mid-term increase that isn't in your agreement, put your position in writing and keep a copy — that record matters far more than what was said on a call.
General information about renting in India, not legal advice. Rules differ by state — check with your local Sub-Registrar office or a lawyer before acting on this.