The contracts are worth $120m for itsGuangdong yard, it said.
It did not name the owner, but it looks likelyto be Chellsea, which ordered two PSVs at Guangdong last year, declaring twoof six options earlier in February.
The owner has also added two more optionsas part of the new deal.
This gives it a potential series of 10vessels.
The latest four are set for delivery from thesecond quarter of 2016 to the first quarter of 2017.
