Turkish pension firm Avivasa debut lifts Sabanci listed firms to 12

(Adds Sabanci details, updates share price)

ISTANBUL, Nov 13 (Reuters) - Avivasa, the Turkish pension joint venture of British insurer Aviva (Other OTC: AIVAF - news) and Turkey's Sabanci Holding, began trading on Thursday, lifting Sabanci's share in Bourse Instanbul to 12 percent of total market capitalisation.

The listing also raised the number of Sabanci companies trading on the exchange to 12, the conglomerate's board chairwoman Guler Sabanci said. Its market share was 9 percent before the float.

Aviva and Sabanci completed the flotation of a 19.7 percent stake in Avivasa on Monday, valuing the firm at 1.68 billion lira ($746 million), in an offering that was almost three times oversubscribed.

Avivasa shares opened up 3.2 percent and were up 0.53 percent at 47.25 lira by 1215 GMT.

Turkey's second-biggest conglomerate, Sabanci group companies include lender Akbank, insurer Ak Sigorta and cement makers Akcansa and Cimsa .

Koc Holding remains Turkey's biggest company, accounting for around 16 percent of total market capitalisation on Bourse Istanbul. It also has 12 listed companies, including refiner Tupras and white goods maker Arcelik (Other OTC: ACKAY - news) .

(Reporting by Can Sezer and Birsen Altayli; Writing by Nick Tattersall and Ece Toksabay; Editing by Jonny Hogg and Susan Thomas)