Mongolia has for decades struggled with endemic graft and the widespread view that the proceeds of a coal mining boom are being hoarded by a wealthy elite has sparked frequent protests and unrest.

Under Prime Minister Luvsannamsrain Oyun-Erdene -- in power since 2021 -- Mongolia has plummeted in Transparency International's Corruption Perceptions Index.

Now fuelling public outrage are allegations that the prime minister's family are enjoying wealth far beyond that expectation of a civil servant on the public dime -- claims sparked by a social media post by his son's girlfriend showing a lavish birthday gift.

In a statement to AFP, the prime minister's office said it "vehemently" denied allegations of impropriety, describing them as a "smear".

But hundreds of mostly young protesters have gathered for eight consecutive days at the capital Ulaanbaatar's Sukhbaatar Square, also known as Genghis Khan square, demanding the premier's resignation.

"The prime minister has to resign," protest organiser O. Ulamsaikhan, 24, told AFP.

"What we are trying to achieve is to establish a new political culture in which unethical behaviour by public officials leads to accountability and resignation," he said.

Also deepening anger in the country are worries over the economy and cost of living. Inflation, which soared following neighbouring Russia's invasion of Ukraine in 2022 -- reached nine percent last year, according to national news agency Montsame.

"Young people are working hard to make a living," said university freshman O. Khulan, 19, who counted among the crowd holding placards declaring "it's easy to resign" and "the natural resources of Mongolia belong to the Mongolians".

"Yet it is unfair that the prime minister's son and his girlfriend have a lavish lifestyle, while I'm buying my bag from a thrift shop," she said.

"The youth are the future of Mongolia, and we have to stand up for a better one. That's why I wanted to come to the protest and express my opinion," she explained.

- Counter protests -

Rejecting the charges, a spokesperson for the prime minister said he is "on record that everyone must live equally before the law and be able to prove their income".

The spokesperson also pointed to efforts by his government to strengthen anti-corruption efforts and more equitably distribute proceeds from the country's vast natural resources.

And counter protesters on the streets of Ulaanbaatar -- overwhelmingly older than their pro-opposition counterparts -- said they supported the prime minister and were sceptical that his resignation would change anything.

"While young people are calling for the prime minister's resignation, it raises an important question: 'What then'?", D. Magsarjav, 65, told AFP.

"I don't think there is a better candidate for the next prime minister," he said.

"It is easy to criticise and call for resignation, but much harder to do the job and deliver results," 63-year-old D. Oyunchimeg added.

But protest organiser Ulamsaikhan vowed to push on with the rallies until Oyun-Erdene steps down.

"We will continue our protest until his resignation."