Activists have obstructed the entrance of a factory in a protest against the arms trade.
Palestine Action and Extinction Rebellion protesters chained the gates at the Elbit Ferranti factory in Oldham, as two others climbed a ledge.
Armed with banners and red paint, they said they oppose "an economy based on devastation, occupation and war".
A Greater Manchester Police spokesman said officers were at the scene and had "engaged with" the protesters.
The Israeli-owned factory, which produces weapons parts and surveillance equipment, has been asked to comment.
The activists also daubed red paint over the windows and sprayed the words "Shut Elbit Down".
The activists have vowed to escalate their action against Elbit until it is shut down for good.
One 37-year-old protester, who gave his name only as Paul, said: "We are not here to be a nuisance but we are here to raise awareness."
The protest comes weeks after the Ministry of Defence confirmed Elbit had won a contract for new "sensor to shoot" system.
The £102m high-end surveillance system will allow British Army soldiers to detect and shoot enemy combatants in seconds.
Speaking after the deal was struck, defence procurement minister Jeremy Quin said: "This contract with Elbit Systems UK not only delivers the very latest in battlefield technology to our frontline soldiers, but also invests in the British defence industry, sustaining more than 500 jobs across the UK."