March 8 (Reuters) - Australian online auto classifieds firm Carsales.com Ltd said on Wednesday it was seeking to raise A$500 million ($329.40 million) to buy an extra 40% stake in Brazil-based automotive digital marketplace Webmotors SA.

The purchase, of about A$353 million from Brazilian lender Santander Brasil SA, will make Carsales a 70% owner of Webmotors, it said. Santander will continue to own the remaining 30% in Webmotors.

"The acquisition is in line with Carsales' strategy of acquiring minority stakes in attractive international markets and moving to control positions over time," the company said.

Carsales.com said it would raise capital via a fully underwritten entitlement offer allowing its existing investors to subscribe for stock at $A19.95 per share. Under terms of the deal, investors can buy one Carsales share for every 14.01 shares they currently own.

The price represents an 11.9% discount to the stock's last closing price.

The company will issue 25.1 million new shares which it said represented about 7% of its current issued capital.

Carsales' deal is the third major one in Australia's capital markets this year after Star Entertainment Group raised A$800 million in February and Flight Centre raised A$180 million in late January.

The deal, seen closing in the fiscal fourth quarter, is not expected to affect earnings per share in the first full year after completion but boost income after that, the company said.

($1 = 1.5179 Australian dollars) ($1 = 1.5181 Australian dollars) (Reporting by Himanshi Akhand in Bengaluru and Scott Murdoch in Sydney; Editing by Maju Samuel and Richard Chang)