Venezuelan president Nicolas Maduro has threatened to seize factories that have stopped production and to jail their owners.
The country is in the midst of a serious economic and political crisis due to the steep fall in the price of oil which has led to opposition demonstrations on the streets.
On Friday, Mr Maduro introduced a 60-day nationwide state of emergency to combat what he called foreign aggression which he also blames for Venezuela's problems.
Opposition leaders said the measure shows the president is panicking as a push for a recall referendum against him gains traction with tired, frustrated Venezuelans.
"We're talking about a desperate president who is putting himself on the margin of legality and constitutionality," said Democratic Unity coalition leader Jesus Torrealba, adding Mr Maduro was losing support within his own bloc.
"If this state of emergency is issued without consulting the National Assembly, we would technically be talking about a self-coup," he told hundreds of supporters who waved Venezuelan flags and chanted "he's going to fall," at a protest rally in Caracas.
The opposition won control of the National Assembly in a December election, propelled by voter anger over product shortages, raging inflation that has decimated salaries, and rampant violent crime, but the legislature has been routinely undercut by the Supreme Court.
Protests are on the rise and a key poll shows nearly 70% of Venezuelans now say Mr Maduro must go this year.
Mr Maduro has vowed to see his term through, however, attacking opposition politicians as coup-mongering elitists seeking to emulate the impeachment of fellow leftist Dilma Rousseff in Brazil.
Saying trouble-makers were fomenting violence to justify a foreign invasion, Mr Maduro ordered military exercises for next weekend.
"We're going to tell imperialism and the international right that the people are present, with their farm instruments in one hand and a gun in the other... to defend this sacred land," he said at a rally.
He added the government would take over idled factories, without providing details.
Critics of Mr Maduro, a former union leader and bus driver, say he should instead focus on people's urgent needs.
The opposition fear authorities are trying to delay a referendum until 2017, when the presidency would fall to the vice president, a post currently held by Socialist Party loyalist Aristobulo Isturiz.
"If you block this democratic path we don't know what might happen in this country," two-time presidential candidate Henrique Capriles said at the demonstration.
"Venezuela is a time bomb that can explode at any given moment."
