MILAN (Reuters) - The main investor in Banca Monte dei Paschi di Siena (>> Banca Monte dei Paschi di Siena SpA) sold another 3 percent stake in Italy's third largest lender to pay off its debts ahead of a 3 billion euro ($4.14 billion) capital increase the bank needs to avert nationalisation.

The Monte dei Paschi foundation, a not-for-profit entity, sold 358.5 million shares between March 19-24 worth a total of 85.7 million euros ($118 million), a share transaction filing showed on Wednesday.

The foundation said on March 18 that it held a 15.07 percent stake in Monte Paschi after selling a separate 12 percent and other small holdings earlier in March. With the latest sale the foundation's stake in the bank falls to around 12 percent.

The foundation declined to comment on the stake sale.

Monte dei Paschi, the world's oldest bank still in business, was bailed out by the state with 4.1 billion euros of aid last year after being hit by the sovereign debt crisis and a derivatives scandal.

It needs to carry out the capital increase to pay back most of the state aid as part of a tough restructuring demanded by the European Commission, or else would face nationalisation.

BLACKROCK INVESTMENT

Monte Paschi Chairman Alessandro Profumo said earlier on Wednesday he hoped the foundation would remain a shareholder.

He also added that he expected its new investor BlackRock (>> BlackRock, Inc.) to subscribe to part of the capital increase, which he expected to be launched in the second half of May.

The asset management company has acquired 5.748 percent of Monte Paschi, a holding that makes it the second-largest investor in the Tuscan bank, a regulatory filing showed last week.

"By definition, those who buy (a stake) today know that there will be a capital increase," Profumo told journalists on the sidelines of an event in Siena. "Those who bought will certainly subscribe to the capital increase."

BlackRock could not immediately be reached for comment.

Profumo added that BlackRock's investments in Monte Paschi and in other Italian banks were a sign that Italy was again attracting investor interest.

In the past month, BlackRock became top investor in UniCredit (>> UniCredit SpA), Italy's biggest bank by assets, and in Intesa Sanpaolo (>> Intesa Sanpaolo SpA), its largest retail bank.

"This sends two important signals: Italy is regaining interest of major players and Monte Paschi is seen as a bank that, as they say, has done its homework," Profumo added.

This sentiment was shared separately on Wednesday by the chairman of Intesa Sanpaolo's supervisory board. "It is an absolutely positive signal and I have heard nothing but positive comments from our shareholders," Giovanni Bazoli said.

In a separate statement, the Monte Paschi foundation confirmed reports of an inspection on Wednesday by market regulator Consob and the financial police.

The operation was related to the foundation's sale of a portion of its stake in the bank earlier this month, it said, adding that it was fully cooperating with the authorities. ($1 = 0.7254 Euros)

(Reporting by Agnieszka Flak, Gianluca Semararo, Silvia Aloisi in Milan, Stefano Bernabei in Rome and Silvia Ognibene in Siena; Editing by Robin Pomeroy)