Shareholders are being urged to be wary of any approach to buy their shares for less than market prices.
Letters have been set to shareholders in major New Zealand companies offering to buy their shares at a significant discount.
One letter, from Carlyle Securities LP, offers to buy Telecom shares for about two-thirds of their market value.
Other low offers have been made by Cargill Securities for shares in Fletcher Building, Nuplex, GPG, Contact Energy and Vector.
Fletcher Building shareholders have been offered $5.64 a share compared with the current price of $7.72.
The company says the offer appears to be an opportunistic bid to buy shares cheaply, and it recommends shareholders reject it.
Fletchers' general manager of investment and media relations, Philip King, says it's the first time the company's shares have been targeted in this way, although the practice is common in Australia.
The NZX is urging shareholders who receive such letters to seek advice. The exchange's market supervision division says people should check the offer price against the market price before agreeing to sell.