Caracas (AFP) - Venezuela's President Nicolas Maduro threatened on Friday to jail his political opponents if they follow through on their vow of launching a legislative trial to remove him from power.

Shrugging off a partially-observed strike which the opposition called to raise pressure on him, the socialist president went on the counterattack.

Maduro sharpened the tone in a volatile political and economic crisis that has sparked food shortages and riots in the South American oil producer.

"If they launch a supposed political trial, which is not in our constitution, the state prosecution service must bring legal action in the courts and put in jail anyone who violates the constitution, even if they are members of Congress," Maduro said in a speech Friday.

Friday's strike was called after authorities blocked a bid by the center right-dominated MUD coalition to hold a referendum on removing Maduro from power.

After that move, the crisis heated up this week. Opposition lawmakers vowed to put Maduro on trial and exchanged accusations of coup-mongering with the mustachioed president.

- Partial strike -

Friday's strike seemed to be only partially observed.

In the capital Caracas and cities such as Maracaibo and San Cristobal, the streets were quieter than normal but public transport was running and banks and some schools opened as usual.

Clashes broke out in recent days between riot police and pro- and anti-government protesters around the country.

Maduro earlier threatened to break the strike by sending the army to take over firms that took part in it.

- Carrot and stick -

The center-right coalition's latest move to pressure the unpopular leftist leader came after anti-government protests drew hundreds of thousands of people on Wednesday.

Maduro vowed to respond forcefully.

But he also extended a carrot to the struggling workers who have served as his socialist party's traditional base: a 40 percent increase in the minimum wage, to the equivalent of about $140 a month.

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But economic analysts called that a drop in the bucket for a country the International Monetary Fund says is facing inflation of 475 percent this year, rising to 1,660 percent next year.

And a wage hike may only add fuel to the inflationary fire.

- 'Attack' on presidency -

Although Venezuela boasts the world's largest oil reserves, falling crude prices have plunged the country into an economic crisis.

Maduro calls the crisis a capitalist conspiracy. The opposition blames his economic policies.

The recession has spawned a messy political battle, after the opposition won a majority in the National Assembly last December.

That forced the president to share power with an opposition legislature for the first time since Maduro's predecessor and mentor, the late socialist firebrand Hugo Chavez, came to power in 1999.

Maduro accuses the National Assembly of staging a "parliamentary coup" by voting to put him on trial for alleged breach of duty.

The opposition says it is Maduro who is staging a coup d'etat by blocking a referendum.

Fears of violent unrest are mounting in the country, where rioting at anti-government protests killed 43 people in 2014.

- Upcoming dialogue? -

The opposition has vowed to march next week on the presidential palace, the scene of a short-lived but deadly opposition coup attempt against Chavez in 2002.

Maduro has said he wants to address the crisis in a "national dialogue" with opponents from Sunday, a plan he claims is backed by Pope Francis.

The MUD said it would agree to talks only if the government respects the constitutional right to a referendum and frees imprisoned activists, among other demands.

It remained unclear whether any talks would go ahead on Sunday.

Also Friday, Venezuela's high court issued a ruling in response to claims from some of Maduro's opponents that he has Colombian nationality, which would disqualify him from being president.

The court said Maduro "is Venezuelan by birth and has no other nationality."