Less than a week after announcing the end of its alliance with Virgin Australia, Air New Zealand has fired the first volley in a trans-Tasman war which will see the former partners become rivals.

The Kiwi carrier says it will "introduce additional services" on the Sydney-Auckland, Melbourne-Auckland and Brisbane-Auckland routes from October 28, 2018 – although details of the new flights and the aircraft they'll use remain to be seen.

Christchurch is also getting a leg-up with two flights per day "on peak days of the week" from both Melbourne and Brisbane, and double-daily services on Monday through Friday from Sydney.

From December 2, 2018 the Star Alliance member is also promising flights "up to five times a week" between Brisbane and Wellington – going up against the current Virgin Australia service – plus seasonal flights "up to four times a week" between Brisbane and Queenstown.

Air New Zealand will begin shifting all passengers booked on its codeshare flights with Virgin Australia after 27 October 2018 onto Air New Zealand services "in the next few weeks", the airline says.

"There is no need for customers to do anything, they will be contacted by either the airline or their booking agent regarding any changes."

Read more: How the Virgin, AirNZ split will affect trans-Tasman travellers