Chile shares post biggest monthly gain in 15 yrs

(Updates with bourse close)

By Alexia Vlahos

SANTIAGO, May 29 (Reuters) - Chilean stocks closed mixed on Friday but blue-chip stocks posted their biggest monthly gain in 15 years, traders said, while the peso closed firmer.

The blue-chip IPSA index .IPSA closed 0.05 percent weaker at 3,100.42 points, preliminary closing data showed, giving up intra-day gains in late trade. The all-market IGPA index .IGPA rose 0.54 percent to 14,684.06 points.

The IPSA, which is up 30.5 percent year-to-date, rose around 16 percent in May, its biggest gain in a single month since January 1994.

Chile's bourse has risen sharply in the past few weeks, led by sectors such as construction, retail and commodities.

"The electrical companies have risen a lot and that is the sector that has pushed the market today," said Felipe Cruz, a trader at the CorpCapital brokerage.

Shares in industrial conglomerate Copec COP.SN, the most heavily weighted company on the bourse, rose 1.36 percent to 7,091.90 pesos a share.

Regional energy group Enersis ENE.SN rose 2.27 percent to 190.29 pesos a share, while electricity generator Endesa Chile END.SN rose 0.64 percent to 824.89 pesos. Power generator AES Gener CHG.SN rose 2.24 percent to 255.57 pesos.