Bermuda-based tanker owner Nordic American Tankers (NAT) has inked a deal with an undisclosed party to acquire four 150,000dwt Suezmax vessels for US$106m.

The company expects that the crude oil tankers, which were built at a Japanese shipyard, will be delivered during May, June and July 2016.

Two ships from the batch were built in 2004, while the other two were built in 2003 and 2000, respectively.

With these vessels, the company's fleet will increase from 26 to 30 vessels.

Due to a strong tanker market seen in 2015, NAT saw its operating cash flow climb by 16 percent to US$57.2m in the fourth quarter of 2015, compared to US$24.5m booked a year ago.