Jamal Juma’ could not help but laugh at one of the accusations he said he had been threatened with while in Israeli detention.

“They said they would indict me for links to Hizbollah. They didn’t like it when I started laughing,” Mr Juma’, a lifelong communist, said on Sunday, five days after his release.

He was talking in an office in Ramallah at the headquarters of the Stop the Wall organisation, of which he is a coordinator. Stop the Wall is a Palestinian grassroots effort dedicated to peaceful and popular resistance against the separation barrier Israel is building up and down the occupied territories.

Mr Juma’ spent 27 days in detention after being arrested at his home in Jerusalem in December. Apart from the threatened charge of links to Hizbollah, Mr Juma’ believed he was to be charged with incitement. But no charge was ever brought and no case was ever heard. “I think they wanted to intimidate me. They threatened me, saying they would harm my reputation, not leave me alone and put me in prison for a long time,” Mr Juma’ said.

He is one of a long-line of grassroots leaders and activists that appear to have been targeted in recent weeks and months for arrest by the Israeli army. Last week alone, 12 Palestinian activists were arrested in three separate army incursions. Since December, the number has risen to the dozens, including a Czech national who was seized from her apartment in Ramallah in the middle of the night and deported.

Jonathan Pollak, an Israeli activist with the Popular Struggle Coordination Committees, said: “It is clear that there are concerted efforts, both on the ground and through legal measures, to take action against the popular movements."

Stop the Wall and Mr Pollak’s group help organise weekly protests against the barrier in Palestinian villages, most famously Bil’in and Ni’lin, where the barbed-wire fence and military-only road cut off villagers from their agricultural land.

Every Friday, a two dozen villagers along with Palestinian, Israeli and international activists brave the tear gas, sound grenades and some times live fire of the Israeli army to break through the barrier and keep the issue alive in both the Israeli courts and the media.

They have had an effect. In Bil’in, for example, constant popular pressure led the Israeli high court in 2007 to order a change of the route of the barrier. It still runs inside occupied territory, however, and the re-routing was ordered only because the court found insufficient security justification for the route as planned.

The Israeli high court has never ruled on the general legality of the barrier that the Israeli government says is intended for security. But Palestinians point out that so far, more than 60 per cent complete, the barrier has left 10 per cent of West Bank territory, including East Jerusalem, between the 1967 borders and the barrier. That, they say, is a blatant land grab.

Indeed, an advisory opinion of the International Court of Justice in The Hague in 2004 found the barrier to be illegal where it dipped into occupied territory.

The nature of the demonstrations against the barrier has also had international resonance. The Elders, a group of former statesmen that includes Jimmy Carter, the former US president, and Desmond Tutu, a South African archbishop, joined the demonstrations, went when they were here. Naomi Klein, the Canadian-American author, also went.

Increasingly, Palestinian politicians are making a point of appearing. Salam Fayyad, the prime minister, has taken part, while Fatah is increasingly beginning to take notice.

Greater fame has come at a price. One person was killed during a demonstration in Bil’in last year, and 32 villagers have been arrested over the past six months alone. Mr Pollak said he was increasingly seeing the Israeli Army employ heavier tactics against activists, including the use of live fire against demonstrators, as well as more arrests and night-time raids into Palestinian villages.

Activists say the stepped-up military action is proof that their strategy of non-violent direct action against the Israeli separation barrier has Israel worried.

“The [popular] movement has become a problem for Israel. Israel believes that by suppressing the movement it will gain more than it loses,” Mr Pollak said.

Mr Juma’ believes his greater international profile helped him when during his detention, which was criticised by, among others, Amnesty International. To charge a man who calls for unarmed and peaceful resistance to a barrier that is illegal under international law with incitement proved difficult even for Israel as a result, Mr Juma’ said.

“This movement is now a Palestinian struggle with international support. Israel can’t stop it and it can’t accuse those working on these campaigns of being terrorists. So now they are trying to intimidate us.”