Striking civil servants who are "seeking justice" fear that unqualified staff may be put in by government to keep Tonga's ports of entry open this week, and they warn that that planes and ships might be stranded.

Meanwhile, airlines and shipping companies have continued to serve Tonga.

The companies were advised in a letter from the Interim Committee for Dissatisfied Civil Servants on Monday, that because of industrial action the Quarantine and Customs operations at the ports of entry throughout Tonga would be closed down from July 25. Both the heads of these two sections are part of the industrial action.

"Please kindly advise your respective counterparts overseas of same to avoid any of your planes and/or ships being stranded here in Tonga," said the letter signed by Maliu Takai, vice chairman, Sione Vuna Fa'otusia, secretary and Mele T. 'Amanaki, assistant secretary of the Interim Committee for Dissatisfied Civil Servants.

They were concerned that unqualified personnel may be put into these operations by government in order to keep the ports open.

"However, for bio-safety and security purposes of the overseas destinations of your planes and/or ships, we advise that the qualifications and experiences of those officers that Government may put in these operations are questioned as all the qualified personnel are part of this industrial action," they advised.

The industrial action continues as the civil servants try to resolve "grievances over the government's new salary structure and subsequent salary adjustments".

"We note with deepest sympathy that our seeking for justice will have a great impact on your operations and we apologise for any inconvenience cause," the Interim Committee said.

Meanwhile, Air New Zealand's flights have arrived and departed as scheduled since the civil servants strike began on Friday. Passenger baggage is being cleared, but there have been problems with commercial cargo, which cannot be cleared at the moment.

The Forum Shipping Agencies expected the Forum Samoa to berth at Nuku'alofa as scheduled early Wednesday morning.