Unite's national secretary Gerard Hehir said the boats were in worldwide waters when they were detained and taken to the southern Israeli port of Ashod.
According to activists, they tried to deliver to Gaza strip medicines, but also urged their governments to demand that Israel lift the blockade.
"There's a Jordanian MP on the other boast, the Awda, and various activists from across Europe", he said, adding that the blockade challenge "is a gesture of solidarity to the Palestinians".
Humanitarian conditions in Gaza have steadily declined in recent years and it's economic state is dire.
Following Al Awda was a Swedish-flagged yacht called Freedom Italy, with 36 activists from 15 different countries, said Zaher Birawi, head of the International Committee for Breaking the Siege of Gaza.
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The vessel Al-Awda, carrying 22 activists from around the world on a humanitarian mission to Gaza, is believed to have been seized by Israeli Defence Forces 48 nautical miles from the Palestinian city.
Dr Wan Azizah, who is also Women, Family and Community Development Minister, said that as such the blockade of Gaza should come to an end and the freedom of movement for all Palestinians must be restored.
It is under the "March of Return" banner that more than 100 Palestinians and one Israeli have been killed in violent clashes with Israeli security forces along the border fence since March 30.
Thew boat was raided by the Israelis on Monday morning, Hehir said. However, the first democratically government of Palestine was not recognised by USA and Israel.
"It is interesting that the two Israeli citizens released on bail have been charged with trying to enter Gaza".
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Other attempts to run the Israeli blockade included a 2016 women's boat with 13 passengers including Nobel Peace Prize victor Mairead Maguire of Northern Ireland. At the time, Israel's foreign ministry said it had provided the flotilla with permission.
The Gaza Strip is controlled by the Islamist militant group Hamas, which has fought three wars against Israel in the decade since taking power there.
"The ship was monitored and was intercepted in accordance with worldwide law".
At least 157 Palestinians have been killed by Israeli fire since then.
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