"This is a secret ballot, and no one should take photographs of their marked or unmarked ballot papers and publish them on social media," the Daily Financial Times reported citing EC Chairman Mahinda Deshapriya as saying on Thursday.
He also advised voters to switch off their mobile phones when entering the polling booth.
A Gazette notification prohibiting such practices was issued by the EC two weeks ago.
Nearly 16 million Sri Lankans will go to the polls on Saturday to elect the eighth President of the country, in an election that will see a record number of 35 candidates in the fray.
This is the highest number of candidates to contest a presidential election in the island nation since the first was held in 1982, and up from 18 candidates who contested the poll in 2015.
The election will also be the most expensive in the country's history, with the EC estimating it to cost a staggering 7.5 billion Sri Lankan rupees ($41 million).
A 26-inch ballot paper, bigger ballot boxes, hundreds of additional personnel on election duty and miscellaneous expenses such as water, telephone, and electricity bills are factors that have pushed the election bill up, the Daily Financial Times quoted Deshapriya as saying.
Meanwhile, campaigning for the election which kicked off on October 8, ended on Wednesday midnight.
The two front-runners in the election are Minister of Housing and Construction Sajith Premadasa, who is contesting from the National Democratic Front (NDF), an alliance led by the ruling United National Party, and former Defence Minister Gotabaya Rajapaksa contesting from the Sri Lanka Podujana Peramuna (SLPP), which was formed last year.
More than 60,000 police personnel have been deployed for election duty, while in some areas members of the armed forces too will on stand-by, the EC said.
Over 100 riot squads would also be on stand-by, while more than 3,000 road blocks will be put up.
Deshapriya said that no major election violence had been reported to date, and the Commission was expecting a peaceful election on Saturday.
He urged political parties to refrain from committing any violations and to ensure a free and fair poll.
( With inputs from IANS )