Tamil Nadu BJP leader S G Suryah was arrested by the police from Chennai late on Friday, with the party's state unit chief K Annamalai slamming the move as an attempt to "curtail free speech."
Police sources said the action was based on a CPI(M) complaint against a social media post of the BJP state secretary.
Suryah was arrested under sections of IPC and the IT Act, police said.
"The arrest of @BJP4TamilNadu State Secretary Thiru @SuryahSG avl is highly condemnable. His only mistake was to expose the nasty double standards of the communists, allies of DMK. Using state machinery to curtail free speech & getting jittery for the slightest criticism is unbecoming of a democratically elected leader and, indeed, are signs of an autocratic leader in the making," Annamalai tweeted.
"These arrests will not deter us & we will continue to be bearers of the uncomfortable truth!" he added.
The BJP state secretary was brought to the Madurai judges' quarters amid heavy security on Saturday morning.