Part of the British convoy preparing to leave London for Gaza
A convoy of 110 vehicles is leaving London for Gaza to deliver £1m of humanitarian aid.
Hundreds of volunteers will act as drivers during the mission, which is organised by umbrella body Viva Palestina and backed by Muslim groups.
Police confirmed that vehicles stopped on the M65 as part of an anti-terror operation were part of the convoy.
Its 5,000-mile route will pass through France, Spain, Morocco, Algeria, Tunisia, Libya and Egypt.
Lancashire Constabulary said several vehicles stopped near Preston were part of the mission.
Three men are currently being held and are being questioned in connection with alleged terrorism offences overseas.
The Gaza Strip is facing a humanitarian crisis following Israel's recent three-week offensive.
About half of Gaza's population is dependent on UN food aid.
Other backers of the mission include the Stop the War Coalition, the Respect Party, the Anglo-Arab Organisation and several UK trade unions.
It will include 12 ambulances, a boat and trucks full of medicines, tools, clothes, blankets and shoe-boxes as well as gifts for children.
Mr Galloway said it would be the largest convoy of British vehicles to north Africa since the days of Field Marshal Montgomery.
"There is an intifada sweeping Britain," he added.
"It is a massive and peaceful movement in support of the beleaguered population of Gaza and Palestine.
"It is happening everywhere, but is especially strong in the north of England and especially among young Muslims."
Jasmine Whitbread, chief executive of Save the Children, said she hoped that the convoy would help raise awareness of the situation in Gaza - but added that far more resources were required to tackle the humanitarian crisis in the territory.
"Around 80 aid trucks are getting into Gaza each day, but we estimate that around 400 are needed daily," she said.
"Some 90% of the population are depending on food aid. Around 100,000 people have been displaced, many of them are now living in tents - the aid is getting through, but much more is needed."