Imagine taking a chunk of rotting corpse from a stagnant sewer, placing it in a blender and spraying the filthy liquid in your face. Your gag reflex goes off the charts and you can't escape, because the nauseating stench persists for days.

This is "skunk", a fearsome but non-lethal tool in Israel's arsenal of weapons for crowd control. It comes in armoured tanker trucks fitted with a cannon that can spray a jet of stinking fluid over crowds who know how to cope with plain old tear gas.

While the army calls skunk an attempt to minimize casualties, rights groups dismiss it as a fig-leaf for the use of deadlier force against protesters in the occupied West Bank.

For although recent years have been among the quietest of the 45-year-old occupation, Israel has been unable to stop an epidemic of local grassroots demonstrations that often turn into clashes.

Skunk is certainly a repellent, but not a complete deterrent. The protesters are fouled but not foiled.

On a Friday in the West Bank's rugged hills, battle lines are drawn for another day of protest.

Gangly Palestinian youths in jeans are ready to let fly stones from homemade slings at Israeli soldiers down the main road of Nabi Saleh village, whose residents demand access to a local spring seized by Israeli settlers.

The soldiers form a phalanx around their curious weapon of war.

"We run away fast when it comes at us, but we don't quit," said a local boy clutching a rock, his dark eyes framed by the oval opening of a black t-shirt wrapped around his face.

"They think they're pretty smart for inventing it, but they still move on to the tear gas, bullets, and breaking into our homes, just the same as usual," he said.

The skunk truck makes its charge, scattering the youths up into the town, where the armed Israelis follow.

"SHIT"

Palestinians call it simply "shit."

"How can you describe this stuff?" said Muad Tamimi, whose gas station on the front line of Nabi Saleh's standoffs is often bathed in it. "It's beyond foul water, like a dead body and rotting food together, which no soap or perfume can take off - I'm hit with it and nobody goes near me for days."

Developed by a private Israeli company and first deployed by the army in 2008, skunk is an organic brew of baking powder, yeast, and some ingredients kept secret. It is harmless to health and designed to reduce casualties, the Israelis say.

"Every attempt is made to minimize the risk of casualties among the rioters, as well as minimizing the risk towards security forces," the army said.

A skunk truck was spotted recently at a base high in the Israeli-occupied Golan Heights, ready to repel any assault on the fence along the disengagement line between Israel and Syria. A rush by Palestinians from Syria caught Israeli troops by surprise last year and they opened fire, killing a dozen people.

Withering Israeli military incursions into West Bank towns have become as much a memory as Palestinian suicide bombings in Israeli cities in recent years. But local protests have continued against land lost to Israel's separation barrier and Israeli settlements on land seized in a 1967 war.

Seventeen Palestinians have been killed in protests since 2004, according to Israeli human rights organization B'Tselem. Scores have been wounded.

CLOSED MILITARY ZONES

The demonstrations play out to a predictable choreography. Many of the young protesters and Israeli soldiers have even come to know each other by name. They use the knowledge mostly to sharpen the taunts they trade about each others' mothers.

Each village has its own script.

In Bil'in, where a court petition by locals reclaimed a portion of the village land from the wall, the fetid stream of skunk now sails at protesters from behind its concrete ramparts. Ultra-Orthodox Jewish settlers in black garb and curls watch the spectacle from atop their settlement homes.

For the army, skunk, and a less-used, focused noise beam called "scream", are proof of defence minister's Ehud Barak's claim that Israel's is "the most moral army in the world", pioneering non-lethal weapons.

"We don't have any intention of harming these civilians," said the army's spokesperson Avital Leibovich. "However, the number of security personnel injured in these riots is actually increasing."

Rights groups question the army's motives, dismissing the rhetoric and the inventions as a public relations ploy to conceal the harsh means used in what they say is a campaign to stamp out legitimate opposition to the occupation.

"Given the exaggerated, unlawful, and dangerous use of tear gas and bullets, we doubt the army's characterization of these events," said Sarit Michaeli of B'Tselem.

Military "Order No. 101," issued the same year Israel seized the West Bank, required political gatherings of more than 10 people to obtain an Israeli permit. It is used to prosecute organizers and proscribe protests before a stone is even thrown.

The legal leeway on the IDF's actions, and its ability to bar and detain activists, are reinforced by the declaration of weekly protest sites as "closed military zones."

"The target is the right to protest, and not much attention is paid to what they're protesting about: the violation of their rights and the taking over of their land and livelihoods," Michaeli said.

Better for the Israelis than using any degree of force would be talks that lead to Palestinian statehood, Palestinians say.

"They should look to granting us our rights, negotiating with us, and paving the way for two states for two peoples," said Shaher Arouri, a lawyer from the al-Haq rights organization.