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SEOUL, July 24 (Reuters) - Shares in Samsung Electronics (005930.KS: Quote, Profile, Research) rose more than 3 percent on Thursday on talk the world's No.1 memory chip maker would announce a share buyback plan at Friday's scheduled quarterly results announcement.

"There is a good chance that Samsung Electronics will unveil share buyback plans tomorrow, as their share prices have suffered steep falls during the latest bearish run," said Suh Do-won, an analyst at Hanwha Securities.

Shares in Samsung, also the world's leading LCD display maker and No. 2 mobile phone manufacturer, had fallen more than 20 percent since mid-May as of Wednesday's closing.

They were up 3.8 percent to 609,000 won by 0423 GMT, leading the wider market's .KS11 1.9 percent gain.

"The buyback size will likely be around 1 trillion won ($991 million)," Suh added.

A Samsung spokesman said he was aware of the market talk, but declined to comment.

Market-watchers said a buy-back would be a positive for shares in South Korea's biggest company.

"Firstly, shares have fallen quite steeply so a buyback is good from both investors' and the company's standpoints. The company can buy its shares back more cheaply and make investors happy at the same time," said a fund manager who asked not to be named.