Norwegian shipowner Arne Blystad has strengthened ties with compatriot Kristian Siem through an increased investment in Siem Offshore.

A filing reveals Blystad’s Songa Capital has struck a deal to buy 10.9m shares in the offshore vessel owner on 13 May.

The investment company’s stake will increase from 1.47% to 6% as a result.

The stake will be worth NOK 174m ($18m) after Oslo-listed Siem Offshore’s stock jumped 21% to NOK 12.18