The election campaign in Philippines took a surprise when Christian group Iglesia ni Christo (INC) endorsed Rodrigo Duterte for president, and Sen. Ferdinand "Bongbong" Marcos for Vice President.

Known for its "bloc voting", INC with 1.7 million church members could be a factor in Monday's tightly contested electoral races.

The Eagle Broadcasting Corp., INC's official media arm said names of the favoured candidates were in the ballots distributed to all members.

Meanwhile, Charismatic group, El Shaddai, maintains freedom of choice among its members rejecting bloc voting.

Administration Party standard-bearer Manuel Roxas II is unfazed by the INC endorsement even as he vowed to continue his fight for decent governance, while the camp of Vice President Jejomar Binay, another presidential hopeful, said they respect the decision of the INC.

INC spokesman Edwil Zabala has been denying reports that their group chose Duterte and Marcos, and even threatened to file charges against those responsible for fueling the news.

The moment we identify the person/s responsible for this fraudulent 'letter' that has gone online bearing the signature of INC Executive Minister Eduardo Manalo, we will charge them in court," Zabala said.

He also denied reports that the INC has endorsed Marcos because of his family ties with the church.  

But an article posted on the official website of the eaglenews.ph  stated that they have already chosen Duterte and Marcos along with 12 senatorial candidates whose names were listed in sample ballots that were "distributed to INC members all over the country."

A copy of sample ballot from the INC containing the candidates' names has leaked online, but Zabala also vigorously denied it.

"In a circular letter read in INC churches, Manalo reminded all the brethren to follow God's teachings on unity when they go to the polls on May 9.