The deal was included in the most recent monthly Airbus order statement, but the name of the airline was withheld.

Airbus declined comment.

No immediate comment was available from VietJet.

Asian demand has been propelling sales of the newest version of Airbus's narrowbody franchise, launched with around 250 orders and commitments in June. In August, Malaysia's AirAsia ordered 30 of the jets as it scaled down an order for the larger A330neo.

VietJet, which has been expanding rapidly in the fast-growing Vietnamese market, has a fleet of 66 Airbus jets. The airline has a domestic market share of 44%, the largest of any Vietnamese carrier, and has been adding more international flights to destinations around Asia.

Airbus may revise up Asian demand in a 20-year forecast due to be published on Wednesday.

(Reporting by Tim Hepher; Editing by Christian Lowe)