Israel on Friday effectively outlawed six prominent Palestinian human rights groups by declaring them terrorist organisations in a major escalation of its decades-long crackdown on political activism in the occupied territories.

The declaration appeared to pave the way for Israel to raid their offices, seize assets, arrest staff and criminalise any public expressions of support for the groups.

Most of the targeted organisations document alleged human rights violations by Israel as well as the Palestinian Authority, both of which routinely detain Palestinian activists.

Israeli and international rights groups condemned the move as an assault on civil society and expressed solidarity with the targeted organisations. Many noted that Israel already outlaws even peaceful political activities in the occupied West Bank. Palestinians want the territory that Israel captured in the 1967 war to form the main part of their future state.

The designated groups are Al-Haq, a human rights group founded in 1979, as well as the Addameer rights group, Defence for Children International-Palestine, the Bisan Centre for Research and Development, the Union of Palestinian Women's Committees and the Union of Agricultural Work Committees.

The Israeli defence ministry said they are secretly linked to the Popular Front for the Liberation of Palestine (PFLP), a secular, left-wing movement with a political party as well as an armed wing that has allegedly carried out deadly attacks against Israelis. Israel and Western countries consider the PFLP a terrorist organisation.

The ministry's statement was released during the Israeli and Palestinian weekend.

Representatives from the targeted organisations could not immediately be reached for comment.

The defense ministry said the organisations are controlled by senior leaders of the PFLP and employ its members, including some who have participated in terror activities.

It said the groups "serve as a central source of financing for the PFLP and had received large sums of money from European countries and international organisations,” without elaborating.

Israel has long accused human rights groups and international bodies of being biased against it and of singling it out while ignoring graver violations by other countries.

The European Union (EU) delegation to the Palestinian territories acknowledged financing activities by some of the groups. It said past allegations of the misuse of EU funds by partners "have not been substantiated”, but that it takes the matter seriously and is looking into it.

"EU funding to Palestinian civil society organisations is an important element of our support for the two-state solution," it said.

The Palestinian Authority condemned what it said was a strategic assault on Palestinian civil society and the Palestinian people's fundamental right to oppose Israel's illegal occupation and expose its continuing crimes.”

New York-based Human Rights Watch and London-based Amnesty International released a joint statement condemning the move as an attack by the Israeli government on the international human rights movement.

For decades, Israeli authorities have systematically sought to muzzle human rights monitoring and punish those who criticise its repressive rule over Palestinians, they said. This decision is an alarming escalation that threatens to shut down the work of Palestine's most prominent civil society organisations.

Israeli human rights group B'Tselem called the government's declaration "an act characteristic of totalitarian regimes, with the clear purpose of shutting down these organisations.”

"BTselem stands in solidarity with our Palestinian colleagues, is proud of our joint work over the years and is steadfast to continue so."