The Communist Party of India (CPI) will picket the Head Post Office here on October 4 demanding the strengthening of the public distribution system (PDS) to deal with the rise in prices of essential commodities. The party will seek food security to all sections of people. The Malampuzha mandalam committee of the party will organise a fast on October 2 at Fort Maidan demanding the setting up of the proposed railway coach factory at Kanjikode for which the foundation stone was laid in February last year, a party statement said here on Saturday.