MANILA - Gay and lesbian groups have called on voters in the Philippines to boycott boxing icon Manny Pacquiao as he bids for a Senate seat, after he described gays as "worse than animals".

An online petition is also underway asking global sportswear company Nike Inc to drop Pacquiao as an endorser. The petition on change.org has garnered more than 2,000 signatures so far.

Pacquiao, revered in the Philippines for winning world boxing titles in eight different weight classes during his 20-year career, suddenly fell from grace after a 30-second interview on local television about same-sex marriage, which he opposes.

"It's just common sense. Do you see any animals of the same sex mating? Animals are better off, they can distinguish between male and female," Pacquiao told TV5 on Monday.

"Now if men are mating with men and women with women, then they are worse than animals," he said.

This is not the first time Pacquiao, a sitting two-term congressman, had earned the ire of the lesbian, gay, bisexual and transgender community for his comments on same-sex marriage. He also apologized for his remarks in 2012.

Same-sex marriage is not allowed in the Philippines where more than 80 percent of the 100 million population is Roman Catholic.

The 37-year old congressman, among those favored to win a Senate seat at the May elections based on independent pollsters' surveys, apologised on Tuesday. Latest surveys showed him in 8th place for the race to win 12 vacant seats in the Senate.

"I'm sorry for hurting people by comparing homosexuals to animals. Please forgive me for those I've hurt," Pacquiao said in a video message on his Twitter account. He said he remained against same-sex marriage.

That didn't stop a torrent of comments on social media lambasting Pacquiao and using the hashtags #NoToManny2016 #zerovoteformanny and #WorseThanAnimals.

"LGBT groups and individuals are saying he should not be voted into office... we are one of them," Danton Remoto, head of Philippine lesbian, gay, bisexual and transgender group Ladlad, or Out, told Reuters by phone.

While the former boxer's comments offended liberal Filipinos, they could have struck a chord with more conservative voters in the staunchly Catholic country.

Local singer Aiza Seguerra, who married her actress-girlfriend partner in late 2014 in San Francisco, also called on voters to boycott Pacquiao.

"You might've done our country proud but with your statement, you just showed the whole country why we shouldn't vote for you," Seguerra said on her Instagram.