* Foreign buying renewed after two selling sessions
* Kia shares boosted on share buyback hopes
* STX shares rally on financial rescue plans
SEOUL, May 14 (Reuters) - South Korean shares rose 1 percent on Tuesday, helped by the return of foreign investors and solid rebounds in auto and technology stocks such as Hyundai Motor and LG Electronics.
The Korea Composite Stock Price Index finished up 20.1 points at 1,968.83 points.
Foreign investors were buyers of a net 160.3 billion won worth of stocks after two sessions of selling.
An unexpected rise in U.S. retail sales in April helped revive foreign interest in South Korean exporters, said Cho Seong-joon, a market analyst at NH Investment & Securities.
Cho added, however, that foreign money flows may change direction at any time, as a share sale by the Vanguard Group will not be concluded until late June.
Vanguard Group, the largest U.S. mutual fund manager, is switching 22 of its biggest index funds away from benchmarks provided by MSCI Inc in order to cut costs.
Exporters rallied, with Kia Motors, which was the fourth most-heavily traded share on the main KOSPI, rising 3.8 percent.
Gains were also fueled by speculation that the company was considering a share buyback worth around 300 billion Korean won ($269.85 million), analysts said.
“A treasury share buyback signals insiders consider the current share price to be undervalued,” said Suh Sung-moon, an analyst at Korea Investment & Securities.
Hyundai Motor shares rose 2.7 percent, snapping two sessions of falls, and LG Electronics advanced 2.8 percent.
Shares in STX Group units rallied after creditor banks came up with an agreement to provide STX Corp, the holding firm of the ailing shipbuilding-to-shipping conglomerate, with a financial rescue.
A KDB official with direct knowledge of the matter said three out of four creditor banks have turned in their agreement to provide STX Corp with 300 billion won in rescue funds.
Shares in STX Offshore & Shipbuilding gained 2 percent and STX Corp ended up 2.7 percent.
Other shipyards also bounced after a streak of declines.
Hyundai Mipo Dockyard gained 4 percent and Hanjin Heavy Industries jumped 5 percent.
Telecommunication stocks continued to rally on expectations their aggressive cuts in marketing costs would help them post strong earnings in the second quarter.
LG Uplus, which saw the biggest turnover in the main KOSPI market, rising 2.9 percent. KT Corp shares rose 1.5 percent.
But other defensive issues underperformed as demand for safer bets waned.
Shares in Lotte Chilsung, a beverage maker, fell 1.8 percent and Orion Corp, a snack manufacturer, fell 1.2 percent.
The KOSPI 200 benchmark of core stocks closed up 1.2 percent, while the junior KOSDAQ fell 0.9 percent.
Move on day +1.03 percent
12-month high 2,042.48 3 January 2013
12-month low 1,758.99 25 July 2012
Change on yr -1.4 percent
All-time high 2,231.47 27 April 2011
All-time low 93.10 6 January 1981 ($1 = 1111.7250 Korean won) (Reporting by Jungyoun Park; Additional reporting by Joyce Lee; Editing by Kim Coghill)