In an initial letter announcing the move and circulated to members of Lae's business community, the union's Lae branch asked members to "move out of the PNGPCL premises and assemble in front of the main gate for briefing."
The Lae Chamber of Commerce and Industry said the strike was in support of landowner companies which have asked PNG Ports to reconsider the international candidates it had shortlisted to operate port facilities in Port Moresby and Lae.
This was confirmed in a follow-up letter, this time directed at the chamber's membership, which said the action was "against the national government's decision to allow a foreign container company to gain control of Lae Tidal Basin port".
The union believes that the appointment of a foreign operator will disadvantage workers under new terms of management, cause them to lose employment benefits to foreign nationals and jobs made redundant under foreign operatorship.
Lae Maritime Workers Union president Samuel Nalau - who signed the aforementioned letter - said the government's "failure and total indifference in addressing our concerns diplomatically" prompted Monday's walkout.
However he also said that a "speedy reaction from the government will see normalcy restored to port operations".
PNG Ports Corporation announced the shortlist mid-October and it includes APM Terminals, Bollore Ports, DP World and ICTSI.
At the time CEO Stanley Alphonse said: "The corporation now looks forward to completing the request-for-proposal process later this year and to finalising details of the management structure that would be needed to develop the terminals which would incorporate a joint venture structure that includes PNG shareholdings.
"It is expected that the combination of local knowledge along with the adaption of the best of overseas and systems practises will significantly optimise operations."
He also said a final selection would be made in the second quarter of 2016.