Carrying party flags and placards, the activists staged a march from Vithalbhai Patel House, close to Parliament House, to hold the demonstration.
The protesters were led by CPI(M) Central Committee member Nilotpal Basu.
CPI(M) General Secretary Prakash Karat later said, "The hike was expected...That's why we said yesterday that the government should not increase the prices...Otherwise we would hold protests all across India.
"We will continue our protests till the government rollbacked the price hike," he said.
In the steepest-ever increase, petrol price was increased by Rs 7.50 a litre with effect from midnight last night.