MILAN, Jan 8 (Reuters) - Italian mid-sized lender BPER Banca said on Monday it had hired banks to sell an 'Additional Tier 1' (AT1) bond, the riskiest type of bank debt, during a busy market session.

BPER said Barclays, the sale's global coordinator, and joint bookrunners Deutsche Bank, IMI-Intesa Sanpaolo, Mediobanca, Morgan Stanley and UBS would sound out investor interest for the bond.

AT1 bonds count towards banks' Tier 1 capital because they are designed in such a way that they can absorb potential losses.

Reuters reported in December that Italian issuers were expected to seize the traditional start of the year momentum on bond markets, including by selling AT1 debt.

On Monday, Italian insurer Generali hired banks to sell a dual-tranche bond that qualifies as a 'green' issuance under the company's framework for social, sustainable and green debt, with maturities of five and 10 years.

Mediobanca is selling a five-year bond, while oil and gas group Eni said it would place 10-year fixed rate debt. (Reporting by Valentina Za, Editing by Louise Heavens)