Screenshots of three ads appearing in WeChat Moments on Jan 25, 2015.

On Sunday night, many WeChat users found in their WeChat Moments news feed an update from a new yet long-awaited friend—advertisement.

The ads, appearing on the second page (one scroll down), look like a regular update from your friends, but with a small "Sponsored" button in the top right corner. Users can turn individual ads off by clicking the button that says "Not Interested".

It's reported that each user will get one new ad every 48 hours, and each ad will remain active for seven days if users interact with them, e.g. clicking, commenting on, or liking the ad. The ads will automatically disappear in six hours if doesn't receive any interaction from the targeted user.

The interactions between the friends of the users and the ads will also be shown. The more likes or comments an ad receives from one's WeChat friends, the more likely he or she will be to see it.

This is not the first time that ads have appeared on the popular social app. The first advert in the Moments was a test by Tencent itself, the Chinese Internet giant that owns WeChat, on Jan 21, 2015.

Tencent has selected 50 brand advertisers for the initial trial, with total ad budget for each exceeding 10 million yuan ($1.6 million), said qq.com, a news portal owned by Tencent.

WeChat, with 468 million monthly active users in the third quarter of last year, estimated in 2014 that the annual income from WeChat Moments news feed ads will reach about 10 billion yuan ($1.6 billion). The minimum price for a WeChat Moments ad campaign is reportedly 5 million yuan. The brands that appeared on Sunday evening included automaker BMW, Chinese smart phone VIVO and Coca Cola.

The ads soon became hot topic among WeChat users. Joke started going around that the ads are distributed based on big data analysis: the rich ones with annual income over 1 million yuan received BMW ads, those who can't afford iPhone 6 but can afford Xiaomi received VIVO ads and those who can't even afford Xiaomi got Coca Cola ads.

Some users think Tencent is clever in promoting the first ads in this way. @Fengguowuhendanhuaerzhidao from Weibo said that after WeChat sent out the ads, many of her friends reposted the ads they received along with the joke.

"I feel optimistic about the ad feed by WeChat and will first consider the platform if I need to make ads for my products," said @Xueshunanbuhaodang.

While other users expressed their dissatisfaction with the ads, saying they infringe privacy and influence user experience.

Last year, WeChat launched an advertising system for Public Accounts that places ads, external links, subscribe buttons and a one-click download button for mobile apps at the bottom of articles published by Public Accounts.