Dozens of demonstrators occupied the roof of the Tel Aviv stock exchange on Thursday morning, Israeli military radio reported, as protests over the high cost of living spread throughout Israel.
Protesters scaled the building a day after the powerful Histadrut labour union threw its support behind the demonstrators, who have set up tent cities across Israel to protest the high cost of housing.
The move puts growing pressure on Israeli Prime Minister Benjamin Netanyahu, who has already been forced to cancel a trip to Poland to address the demonstrators, offering them reforms that they rejected as insufficient.
Histadrut said it was issuing Netanyahu with an ultimatum.
"If by Saturday evening, the prime minister has failed to meet with our secretary general Ofer Eini to discuss solutions to lift this social crisis, Histadrut will use all means at our disposal to support the demands of the protesters," a spokeswoman for the union told AFP.
She declined to say whether Histadrut would call on its members to join a general strike announced by Israel's Union of Local Authorities on Wednesday.
The August 1 one-day strike will see local authority offices shut down and rubbish collections halted.
One of the protesters involved in occupying the roof of the Tel Aviv stock exchange told military radio it was a symbolic gesture intended to draw attention to inequalities in Israeli society.
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"Ten big companies control 80 percent of the stock market and take all the fruits of the growth in the national economy," he said.
Since 2004, Israel's economic growth rate has averaged 4.5 percent, while unemployment has fallen to around six percent from close to 11 percent over the same period.
But the gaps between Israel's rich and poor are among the widest in the Western world. In 2011, Israel ranked fifth for unequal income distribution among the 34 member states of the Organisation for Economic Cooperation and Development.
This summer, Israelis have been showing their anger over the situation, beginning with a boycott of their much-loved cottage cheese in a successful bid to bring down the rising cost of the food item.
Then, in mid-July, students and other young protesters began pitching tents in the middle of Tel Aviv to protest the high cost of housing, quickly winning supporters and sparking similar tent protests in other Israeli cities.
Over the weekend, tens of thousands of people rallied in support of the protest in Tel Aviv, and several thousand also protested in Jerusalem.
Such widespread social upheaval has not been seen in Israel since the early 1970s when thousands of people, led by a group called the Black Panthers, took to the streets to protest against racial discrimination suffered by Mizrahi Jews of Middle Eastern descent.
Alongside the housing protest, Israel's doctors are stepping up a long-running strike over pay and conditions, with medics announcing plans for a series of wildcat strikes in public hospitals.
Senior members of the Israel Medical Association are marching from Tel Aviv to Jerusalem in protest, and plan to arrive on Friday to present Netanyahu with a petition signed by tens of thousands of people.