* Bank re-assessing cash call in light of EU health check
* Capital hike may increase to 5 bln euros - media report
* Bank aims to repay state aid this year
* Shares fall 10.4 percent (Repeats with link to Breakingviews)
MILAN/ROME, April 15 (Reuters) - Italy's loss-making Banca Monte dei Paschi di Siena is considering increasing the size of its planned share sale to help it pass a Europe-wide bank health check and repay state aid this year.
Italian banks, struggling under a mountain of bad debt after two years of deep recession, are aiming to boost their capital bases to cover loan losses and meet a tough assessment of asset quality being carried out by the European Central Bank.
Eight Italian banks including Monte dei Paschi di Siena, the third-largest, have already announced they will seek to raise 8 billion euros ($11 billion) of additional capital over the coming months.
Monte dei Paschi, which was rescued by the government last year, was expected to launch its fundraising late in May. But an increase in the size of the rights issue would delay the exercise to June or later, pushing the Tuscan bank to the back of the queue of Italian lenders asking shareholders for money.
Late on Monday, news agency ANSA said the bank was now looking to tap investors for up to 5 billion euros, two thirds more than the 3 billion initially planned. Monte dei Paschi's market value is 2.9 billion euros at the current share price.
On Tuesday, Monte dei Paschi said it was evaluating how much capital it needed in light of the ECB's asset review and also after discussions with Italy's banking supervisor, the Bank of Italy. It declined to confirm whether it was aiming to raise 5 billion euros.
"The bank is assessing the implications in relation to the amount of funds necessary to pay back this year's state-aid as pledged with the European Commission," it said.
Monte Paschi had already planned to pay back this year 3 billion of the 4.1 billion euro state bailout it has received.
The Bank of Italy declined to comment.
Monte Paschi's shares fell 10.4 percent on Tuesday to 0.2248 euro in heavy volume of 1.1 billion shares, equivalent to around 9 percent of the bank's capital.
Davide Serra, the founder of hedge fund Algebris and a former banking analyst, told Italy's Radio24 earlier this month that Monte dei Paschi could need to raise as much as 6 billion euros if it decided to bolster its coverage of doubtful loans in line with bigger rivals UniCredit and Intesa Sanpaolo .
These two banks set aside a combined 21 billion euros in 2013 to cover for losses, compared with 2.75 billion euros at Monte dei Paschi.
"If you were to apply the same level of coverage of Italy's No.1 and No. 2 bank, Monte dei Paschi would need a further 3 billion euros of capital," Serra told Radio24.
Broker Fidentiis said in a note to clients that additional capital may be needed for the bank to further clean up its balance sheet and to pay back all of the state aid.
The bank was bailed out last year after it suffered heavy losses in the euro zone debt crisis and was hit by a derivatives scandal.
It was unclear what implications a larger capital increase would have on a shareholder pact recently signed between the Monte dei Paschi foundation, the former controlling investor, and Latin American investors BGT Pactual and Fintech.
Together, these three investors control 9 percent of Monte dei Paschi and have pledged to keep the same holding after the capital hike. ($1 = 0.7238 Euros) (Additional reporting by Valentina Za and Stephen Jewkes; Editing by Erica Billingham)