A New Zealand union boss has been detained in Israel after he took part in an aid convoy to Gaza.

Unite Union leader Mike Treen was allegedly attacked alongside other international campaigners on the ship Al Awda on Monday (local time).

The union says Mr Treen was there on a peaceful mission and is is calling on the Government to intervene.

"Mike was taking part in a peaceful mission to deliver aid to Gaza and was in international waters when attacked and detained. We understand he has been taken, kidnapped in reality, to the southern Israeli port of Ashod," said National Secretary Gerard Hehir.

"We expect the New Zealand Government to strongly protest and demand his immediate release, along with his fellow campaigners and the Al Awda so they can deliver the much needed medical aid to the port of Gaza."

Mr Treen has been detained in similar circumstances to Green Party co-leader Marama Davidson.

Ms Davidson was among a number of others on the Women's Peace Flotilla which left for Gaza on September 21, 2016 to protest Israel's decade-long blockade.

She was one of 13 women aboard the Zaytouna-Olivia which was intercepted in international water and towed to Ashod by the Israeli navy.

Ms Davidson has called for the Government to intervene in Mr Treen's detainment.

"I will always be grateful that I had the opportunity to be part of the women's peace boat to Gaza in 2016 and I hope Mike fares well," she wrote on Facebook.

"He is a staunch advocate for peace through justice and will have an important story to tell the world."