* Tencent down 4.51 pct at midday vs benchmark's 2.81 fall
* Decline follows 5 pct fall on Thursday
* Top shareholder Naspers to sell 2 pct of stake
* Firm reported profit beat estimates, revenue missed (Adds share update, Tencent and analyst comments)
HONG KONG, March 23 (Reuters) - China's Tencent Holdings Ltd saw its shares down 4.51 percent at the midday trading break on Friday after the internet firm's largest shareholder, Naspers Ltd, said it would lower its stake for the first time in 17 years.
The Hong Kong-listed stock opened 7.8 percent lower at HK$405, its lowest opening price since Feb. 9, before regaining ground to HK$419.6 by noon. The benchmark Hang Seng Index was down 2.81 percent.
A day earlier, the stock fell 5 percent following Tencent's late Wednesday report showing quarterly revenue missed estimates as well as expectations of margin pressure, although profit beat forecasts.
Friday's decline wiped $24 billion off Tencent's market value, though at $508 billion, it is still Asia's most valuable listed company and fifth globally behind Apple Inc, Alphabet Inc, Amazon.com Inc and Microsoft Corp.
South African media and e-commerce group Naspers said on Thursday it planned to sell up to 190 million Tencent shares, or 2 percent of its holding, in a sale that could earn Naspers up to $11 billion. It also said it had no plans to further reduce its holding for the next three years.
"The funds will reinforce Naspers' balance sheet and be invested in classifieds, online food delivery and fintech globally," said CICC analyst Natalie Wu. "We think it is a good opportunity to buy into dips given Tencent's solid fundamentals."
Jefferies analyst Karen Chan said, "Given Naspers' largest single shareholding and board representation in Tencent, we believe its stake sale is unlikely to be a reaction to Tencent's quarterly results. Instead of a timed profit-taking move, we believe this is more to improve Naspers' own free cash flow and allow it higher flexibility in pursuing investment opportunities."
A Tencent spokeswoman said it was informed and supportive of Naspers' decision, and that Naspers' intention to keep its remaining stake for the next three years demonstrated its confidence in Tencent.
(Reporting by Sijia Jiang and Donny Kwok Editing by Paul Tait and Christopher Cushing)