* Shares priced at 68 Sfr, mid-point of price range - sources
* Transaction size increased by 300 mln Sfr - sources
* Shares to start trading Friday
* Sunrise to start trading with discount to peer Swisscom - source (Adds details, quotes)
By Oliver Hirt and Rupert Pretterklieber
ZURICH, Feb 5 (Reuters) - Swiss telecoms firm Sunrise increased the size of its stock market listing by roughly a fifth because of strong investor demand and will price its shares at 68 Swiss francs ($73) apiece, three sources familiar with the transaction said on Thursday.
Sunrise, backed by European private equity fund CVC, last week set a price range of 58-78 francs per share and later narrowed the range to 65-70 francs. Shares are set to start trading on Friday
"We had very strong demand and have therefore increased the transaction by about 300 million francs," one of the sources said, adding Switzerland's biggest flotation since 2006 would now raise 2.3 billion francs including an overallotment option.
"Equities markets are in very good shape and the long time span of the ECB's liquidity operation (QE) is outweighing concerns over Greece," another of the sources said.
The market capitalisation of Sunrise, which is using Swiss tennis star Roger Federer to promote its brand, will be 3.1 billion Swiss francs in the IPO. Seventy four percent of the shares will be in free float after the listing.
The company itself will reap 1.3 billion francs from selling new shares and plans to use the proceeds to pay down debt and step up its challenge to incumbent Swisscom .
Both Sunrise and rival Orange Switzerland have struggled to wrest market share from government-backed Swisscom. They have toyed with a merger in the past, but the plan was blocked by Swiss competition regulators in 2010.
Industry sources have said a tie-up could now be viewed more favourably by regulators, as a bigger firm could improve investment and consumer choice in "converged" services that offer both mobile and fixed-line products.
Sunrise will start trading at a discount to Swisscom, which the stock market values at about 8.2 times its expected 2015 earnings before interest, tax, depreciation and amortisation (EBITDA), including debt.
"Based on an 2015 EBITDA estimate of 650 million francs, Sunrise will start trading at a multiple of 7.4," one of the sources said.
Sunrise had earnings before interest, tax, depreciation and amortisation (EBITDA) of 621 million francs in the 12 months to September. ($1 = 0.9276 Swiss francs) (additional reporting by Arno Schuetze; Editing by Ludwig Burger)