(Adds Boral statement, background, shares)

July 6 (Reuters) - Diversified Australian investor Seven Group on Tuesday raised its buyout offer for Boral to A$7.40 per share, its latest bid in a near two-month long battle to take full control of the building materials supplier.

Seven Group sweetened the offer by 10 cents and called it the "best and final" price, valuing Boral at A$8.75 billion ($6.64 billion). The new offer, however, was swiftly rejected by Boral again, saying it undervalued the company.

The latest offer is also well below the value of A$8.25-A$9.13 per share estimated by an independent expert last month.

The interest in Boral has gained traction as it benefits from a strengthening Australian real estate market, with property prices hitting record highs due to monetary and fiscal stimulus. Its stock has surged 50% so far this year and closed marginally higher at A$7.38 on Tuesday.

Seven, which invests in mining, energy and media companies, has been steadily building its stake in Boral over the past 15 months, bringing it up to 34.5% stake as of July 6. Shares of Seven Group closed 2.4% lower.

The sweetened offer was unconditional and scheduled to close on July 15, Seven said.

($1 = 1.3179 Australian dollars) (Reporting by Sameer Manekar, additional reporting by Vasudha Kaukuntla in Bengaluru; editing by Uttaresh.V)