New Zealand shares tumbled Monday as did most equities in Asia as US tariffs on Canadian, Mexican, and Chinese goods started to kick in and triggered the start of a trade war among the world's largest economies.

The S&P/NZX 50 Index fell 1.4%, or 184.69 points, to close at 12,810.32.

Other Asia-Pacific shares were also in the red, with Japan's Nikkei 225 tumbling 2.7%, Hong Kong's Hang Seng down 0.7%, and Australia's ASX 200 losing 1.7%. Mainland Chinese markets are closed until Tuesday for the Lunar New Year.

On Feb. 1, US President Donald Trump signed executive orders imposing a 25% tariff on goods from Canada and Mexico, and a further 10% levy on Chinese goods. Trump slapped a lower 10% tariff against imported Canadian oil.

Canada and Mexico announced their retaliatory tariffs, while China said it would take the case to the World Trade Organization without specifying any countermeasures.

In domestic news, the household cost of living in New Zealand rose 3% in the 12 months to the December 2024 quarter, following a 3.8% increase in the year to the September quarter, Stats NZ data showed Monday.

In corporate news, Fisher & Paykel Healthcare (NZE:FPH, ASX:FPH) warned that its costs are likely to increase in fiscal 2026 due to new US tariffs, which could add two to three years to the expectation of reaching a gross margin target of 65%. The company's shares finished nearly 7% lower.

Elsewhere, Rakon (NZE:RAK) will transition to a market-based business structure, effective immediately, under its strategic organizational transformation.