The company purchased another 3.77 million of HMM's shares for US$76.6 million, taking the Samra Midas (SM) group's stake to 6.29 per cent.

Other SM companies, such as Korea Shipping Corporation, Korea Line Corporation (KLC), and STX Construction acquired HMM shares in a massive stock purchase on June 20.

Cross-affiliate holdings are common in South Korea and are commonly viewed as a tactic for owners of local conglomerates to maintain control.

The SM group's original business is construction, but its interest in shipping began in 2013 with its acquisition of KLC.

An SM Line representative said its continuing purchasing of HMM's shares was purely an investment and it had no ambitions to acquire HMM.

SM Group remains HMM's third-largest shareholder, behind state-backed Korea Development Bank (KDB) at 20.69 per cent and Korea Ocean Business Corp at 19.95 per cent.

"South Korea has a plethora of carriers, but these two [HMM and SM] have the widest reach, geographically, so I can see why the speculation is brewing. Whether it is practical or not probably depends on SM's resources. As the industry has boomed, so too has HMM's valuation," said Drewry contained research senior manager Simon Heaney.

Separately, SM Line announced that it enhanced its Pacific Northwest (PNS) Service, which calls at Busan, Gwangyang, Yantian, Shanghai, Ningbo, Vancouver, Seattle and Portland.

"Calling at Prince Rupert will not only contribute to securing additional US and Canadian inland cargo but will also greatly help maintain punctuality due to the low congestion around the port."