On the day he was officially proclaimed as one of 12 senators-elect in the Philippines, world boxing superstar Manny Pacquiao said Thursday he favours restoring the death penalty in his country for drug-related and other serious crimes.

"In the eyes of God, it is not unlawful," the 37-year-old born-again Christian, pastor and two-term congressman said of capital punishment, Reuters reports.

His view supports that of tough-talking President-elect Rodrigo Duterte who has said that he will ask Congress to re-introduce the death penalty that was repealed in 2006.

However, Pacquiao said he opposes any proposed divorce bill, according to the Philippine Daily Inquirer.

He said the first bill he will file when Senate session begins would be to provide free elementary-to-college education for children from impoverished families.

Pacquiao ran for a Senate seat under the ticket of a losing presidential candidate, Jejomar Binay. However, he was also endorsed by Duterte.

During his senatorial campaign, the Bible-quoting boxer turned lawmaker suffered a huge drop in support in February when he described people in same-sex relations as "worse than animals."

His comment sparked a global backlash, prompting Pacquiao to apologise. However, he made clear that he opposes same-sex marriage.

During the proclamation of the 12 winning senators at a ceremony in Manila, Pacquiao pledged to serve "the poor and downtrodden masses."

Pacquiao, the former eight-time world boxing champion, was the seventh placer among the top-12 Senate vote getters.

In his speech, Pacquiao noted that the results of the May 9 election showed that "Filipinos want their government back in the hands of the ordinary people. They want a new set of leaders who would stand up for their aspirations and share their goals."

He said the victory was not his but that of the Filipino people. "For the millions of common folks who believe in my capacity to put into words what they cannot express; to champion the causes closest to their hearts; and to serve them in a higher and greater platform, you have just won a seat in the Senate," he said. "My dearest [countrymen], the victory is really yours."

Pacquiao then made a solemn vow: "I will not let you down. I will not steal from you. I will not fail you. Rest assured I do everything for God and our country."