Foreign Affairs Minister Winston Peters has condemned the recent seizure of two oil tankers in the Strait of Hormuz as "an inexcusable violation of international law".
Last week, Iran seized a British-flagged oil tanker and a Liberian-flagged oil tanker - both had mixed nationalities on board. The owner of the Liberian-flagged tanker later said the ship was briefly boarded by armed guards before being allowed to go.
Afterward, though, US Central Command said it began extra US aerial patrols.
"The seizure of commercial ships in this important transit lane is an inexcusable violation of international law, including the freedom of navigation," Mr Peters said in a statement today.
"Iran’s recent actions risk escalating a dangerous situation in the Gulf region. We call on Iran to release the detained vessels and to engage with the international community in steps that help reduce tensions and the prospect of conflict."
He said officials from the Ministry of Foreign Affairs and Trade have communicated New Zealand’s concerns to the Iranian Embassy in Wellington.
Meanwhile, the US military intends to protect American commercial ships against Iranian threats in the Persian Gulf and Strait of Hormuz but will not provide naval escorts in every case, the newly installed defense secretary said today.
The aim of the US naval and air presence in the Gulf area is to deter Iran from threatening to stop or seize any American commercial ship, Mark Esper told reporters on his first full day as Pentagon chief.
Esper, who previously served as the Army's top civilian official, was confirmed by the Senate and sworn at the White House yesterday, ending a seven-month absence of a confirmed defense secretary.
The Associated Press contributed to this report.