Namibia's First Lady, Monica Geingos, marked International Women's Day with a powerful message to internet trolls, who she says have hurled insults at her on social media.

"I've decided that enough is enough... I will not be silenced anymore," Geingos said in a video posted on social media Monday.

"I recently instituted defamation lawsuit against this type of behavior..," she added.

The 44-year-old said she has frequently been subjected to "slut-shaming," and has been labeled as "fat, ugly, stupid and too ambitious" by cyber bullies.

Geingos is the third wife of Namibian President Hage Geingob, 79.

They married in 2015 and have no children."When they are not asking when or if my husband will impregnate me.... When I'm not 'busy being a manipulative, deceitful gold-digger,'

I am 'busy running the country' as I have 'bewitched my old Sugar Daddy husband' who is 'too blind to see through my feminine charms,'" Geingos said in the video which has gone viral.

Geingos charged women to speak up for themselves when harassed and posted the video online using the hashtag #YourSilenceWillNotProtectYou.

"When you stand up for yourself... You will be called a troublemaker, too aggressive, too unladylike. That is why many of us prefer not to challenge gender bias. That's why we endure being called gold-diggers, sluts... Too fat or too thin," she said.

The First Lady highlighted a series of abusive tweets directed at her in the video. Mwahangange Kondja's tweet was one of those featured.

He told CNN Tuesday that Geingos was being targeted by trolls because of her age.

"I have to give my unbiased opinion, even though she used a screenshot of my tweet from my old account and made it look like I was being misogynistic. I cannot deny the misogyny and insults hurled at her.

"There's clear misogyny from young people towards her perhaps because of being young herself, so they see her as a peer of some sort," Kondja told CNN.

Geingos was rated one of Namibia's most influential people before her marriage to Geingob, who had previously served as the country's prime minister.