MANILA - The website of the Movie and Television Review and Classification Board (MTRCB) was defaced by hackers on Saturday over the airing of a negative political advertisement on television.

The cyber attack, which appears to have been perpetrated by "Pinoy Hackers," happened following the release of a negative ad against presidential race frontrunner Davao City Mayor Rodrigo Duterte.

In its message, the group lambasted the MTRCB for allegedly turning a blind eye to what it called a "malicious political mudslinging ad."

An ad paid for by Senator Antonio Trillanes IV, aired on ABS-CBN, targeted the Davao City mayor, showing children reacting to some of Duterte's controversial remarks and acts, including his cursing of Pope Francis and his comment about the rape-slay of an Australian missionary.

A different negative ad about Duterte also aired on GMA Network.

"Naglabas ng isang paid ad ang isang politiko at ito ay ipinakalat ng isang news giant. Anong nangyari sa taga-monitor, taga-salang at taga-bantay ng mga ipinopost sa TV at sa print media?" the Pinoy Hackers said.

"Ginawa itong MTRCB para magsilbing taga-implementa ng 'FAIR AND UNBIASED' reporting ng mga TV, print and movie industry pero nagsawalang-kibo (literal, they turned a BLIND EYE) to that malicious political mudslinging ad.

"Ano pang silbi mo MTRCB? Isa ka din ba sa mga simpleng nagpapalamon sa pera ng bayan?" the group added.

The MTRCB, in a Twitter post on Friday, said it is the Commission on Elections (Comelec) which has sole jurisdiction to regulate political TV ads under the Fair Elections Act.

Comelec spokesperson James Jimenez, however, said the poll body can only monitor the duration of an ad on a per station basis and has no power to censor its contents.

Jimenez added that airing of political ads against a candidate is not against the law.

READ: Comelec: Negative pol ads allowed by law

In a statement, ABS-CBN stressed that it had nothing to do with the production of the political ad, and that it was "duty bound to air a legitimate ad."

"The controversial political advertisement being talked about in social media, which aired on ABS-CBN, was produced and paid for by Sen. Antonio Trillanes IV. Prior to the airing, ABS-CBN’s ethics committee reviewed the content of the material, which complies with the requirements of pertinent election laws," the company said.

ABS-CBN pointed out that Comelec guidelines prohibit radio and television stations from discriminating against any candidate or political party in the sale of air time.

"By airing the said commercial, ABS-CBN is being consistent with COMELEC guidelines, which prohibit radio or television stations to discriminate in the sale of air time against any political party or candidate. We are duty bound to air a legitimate ad."

The running mate of Duterte, Senator Alan Peter Cayetano, on Friday said he has secured a temporary restraining order (TRO) from a Taguig court against the negative ad. The TRO is for 72 hours or 3 days.

READ: Cayetano gets TRO vs anti-Duterte ad

Cayetano said the "malicious" ad is the latest black propaganda hatched by a conspiracy composed of Malacañang, Liberal Party (LP) standard bearer Mar Roxas and Senator Grace Poe.

Communications Secretary Sonny Coloma, however, denied Cayetano's allegations, saying the Palace is focused on conducting clean elections.