LONDON/MILAN, Nov 23 (Reuters) - Prima Assicurazioni, an insurance start-up backed by some of the world's largest private equity firms, is seeking indicative offers this week to bring in a new minority investor and raise fresh cash, two people close to the matter told Reuters.

A deal could value Prima Assicurazioni, which sells online motor and home insurance policies supplied by third parties, at around 1 billion euros ($1.1 billion), one of the people said.

Prima, which has more power than an ordinary insurance agent because it can set quotes for its partners' policies, uses technology such as big data analytics to grow in a market which traditionally has a big protection gap.

Premiums grew 31% last year to 660 million euros, the company reported.

The Milan-based group has been sounding out other private equity investors to inject capital to support its growth, said the people, who spoke on condition of anonymity.

Existing shareholders may sell a slice of their holdings as part of the capital increase, the people said.

Co-founder Teodoro D'Ambrosio is the group's largest shareholder, with Blackstone, Goldman Sachs and Carlyle also holding stakes, a Prima spokesperson said, declining to comment on the fundraise.

The efforts come at a time when private equity activity is down, amid difficult market conditions and pressure to return capital to fund investors.

Blackstone, Carlyle and Goldman Sachs declined to comment.

Founded in 2015, Prima Assicurazioni offers online insurance products to consumers in partnership with Munich Re and Swiss Re.

It controls nearly a third of Italy's online motor insurance market and is expanding into Spain and Britain, according to a recent press release.

Prima Assicurazioni was reported in the Italian press earlier this year to have appointed bankers at JPMorgan to raise capital. JPMorgan declined to comment. ($1 = 0.9168 euros) (Reporting by Pablo Mayo Cerqueiro in London, Valentina Za in Milan and Amy-Jo Crowley in London; Editing by Anousha Sakoui and David Evans)