In one of the biggest supermarkets in Harare, Zimbabwe's capital, cooking oil, rice and Coca-Cola are all out of stock while a notice on the bread rack tells shoppers they can only buy one loaf each.Outside, a small crowd mills around hoping for a delivery of goods that may never come.A currency crunch and a new tax on electronic transactions has spawned fears that Zimbabwe's wrecked economy is about to endure a fresh bout of chaos."It looks like we are heading back to 2008," said Pardon Muringani, a shopper in OK Supermarket, recalling how shops ran out of goods when hyperinflation peaked, destroying savings and forcing the country to abandon the Zimbabwe dollar. "We just hope a solution is found soon, so that we don't get there," he said.President Emmerson Mnangagwa took over from veteran autocrat Robert Mugabe last year and won disputed elections in July.Mnangagwa had campaigned on a pledge to revive the economy, attract foreign investment and create jobs.But less than three months after the vote, the dire financial problems of the Mugabe era have returned to haunt the new leader.The latest crisis erupted last week when Finance Minister Mthuli Ncube announced a two-percent tax on all electronic transactions to increase revenue.Many Zimbabweans rely on electronic payments as US dollars, which function as the main currency, are scarce, and the local "bond note" currency is little trusted.President calls for calm Mnangagwa urged citizens to stay calm as drivers queued for hours for rationed petrol and those with money stock-piled any food for sale.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. "There is no need to panic. The government is guaranteeing the availability of all essential commodities including fuel," he said in a statement. "The road is long, winding and at times bumpy but there is no other way."The shortages have created a thriving black market, with a litre of cooking oil being sold on the street for up to $12 instead of $3.70."Measures should be taken. We can't continue like this," Yvonne Makoni, a property consultant, told AFP while waiting for petrol. Often each driver can fill up with only 20 litres and must pay cash.A local franchise of Kentucky Fried Chicken has shut its restaurants, posting signs on the doors saying it was unable to buy meat without US dollars, while other food outlets have followed suit.Many pharmacies have also shut. Those still open often cannot offer essential medicine for chronic conditions like diabetes and hypertension."We don't manufacture many drugs. We have to import these and we need foreign currency," Luckymore Bhunu, secretary for the Retail Pharmacists Association, told AFP.Many other shops have been closed in the capital and second city Bulawayo in recent days.National strike planned The main trade union has called for a national strike on Thursday over the country's renewed economic woes - though police have banned marches in Harare due to a cholera outbreak."Price madness: Govt intervenes," blared the headline in the state-owned Herald newspaper on Wednesday, with the main article accusing retailers of triggering stock-piling and shortages by raising prices."As a result of lack of confidence, we see panic buying of commodities including fuel," Prosper Chitambara, of the Labour and Economic Development Research Institute of Zimbabwe, told AFP."Businesses that need to acquire foreign currency have to go to the black market where premiums are 200%." Bond notes were introduced in 2016 - in theory equal to the US dollar, but they were soon trading at a far weaker rate, and the gap has widened in recent weeks. Unemployment over 90% Public anger at the state of the economy was a contributory factor in November's military intervention that finally toppled Mugabe, then 93, after 37 years in office.Mugabe's reign as the head of the ruling Zanu-PF party was marked by corruption and mismanagement that led to an exodus of investors, mass emigration and collapse of many public services.Unemployment is generally put at over 90%, while the size of the economy has halved since 2000 when many white-owned farms were seized."The crisis has gone beyond Zanu-PF's capacity to (cope)," said Jacob Mafume, spokesperson for the opposition MDC."We cannot be silent and pretend all is well while the people endure incessant suffering."