Offshore marine group Otto Marine has agreed to sell two anchor handling tug supply vessels to an undisclosed third-party buyer for US$170 million (S$214.9 million).

Once the sale is completed, the vessels will be chartered back by Otto Marine's wholly-owned subsidiary, Otto Fleet, for eight years, the company said on Monday.

The vessels will in turn be hired from Otto Fleet by another Otto Marine susbidiary, Go Offshore (Asia), on a time-charter of two years.

The two vessels are currently under construction at Otto Marine's shipyard in Batam, Indonesia, and will be handed over to the buyer after the completion of legal documentation and a final inspection.

The transactions are expected to have a positive impact on Otto Marine's consolidated net tangible assets per share or earnings per share for the financial year ending Dec 31 this year, the company said.