A flotilla of boats headed for Gaza carrying 350 pro-Palestinian activists - including climate change campaigner Greta Thunberg - has departed from Barcelona.
Around 20 vessels displaying Palestinian flags left the Spanish port at 19:00 local time on Monday, stocked with medical and food supplies.
The flotilla first attempted to set sail on Sunday, but had to return to port due to stormy weather.
The aim of the mission is to break Israel's illegal siege on Gaza, the organizers said - though a previous attempt to reach Gaza by sea was intercepted by Israeli forces.
The Global Sumud Flotilla Mission plans to launch in two waves - the first from Barcelona and the second from Tunis on 4 September.
Activists hope the boats will converge in the Mediterranean before sailing towards Gaza, a trip that is estimated to take seven or eight days.
We are sailing again to break the siege and open up a humanitarian corridor, Thunberg said in a video message.
Punk singer Bob Vylan - who provoked controversy for leading a chant of death to the IDF [Israel Defence Forces] at Glastonbury - spoke at the flotilla's departure on Sunday, calling the activists brave individuals attempting to push for government action.
Israeli authorities have characterized a previous attempt to sail aid to Gaza as a publicity stunt offering no real humanitarian assistance. In March, Israel imposed a nearly three-month blockade on goods entering Gaza, before partially lifting it in late-May following international pressure. A UN-backed body has since declared there is a famine in parts of Gaza.
Israel has attempted to impose its own distribution system through the controversial Gaza Humanitarian Foundation, criticized by aid agencies.
In June, a yacht carrying Thunberg and other activists was intercepted by Israeli forces trying to reach Gaza and subsequently deported.
In 2010, Israeli commandos killed 10 people during a raid on a Turkish aid flotilla trying to reach Gaza.
