"This is an attack against President Nicolas Maduro," Communication Minister Jorge Rodriguez said following the incident that was caught during a live broadcast.

State television images showed Maduro looking up in confusion mid-speech as a bang is heard, then uniformed members of Venezuela's National Guard lined up in a parade suddenly breaking ranks and scattering.

Rodriguez said there was "an explosive charge... detonated close to the presidential podium" and in several other spots along the parade held in central Caracas.

Maduro "came out of it completely unharmed and at this moment is carrying out his normal duties and is in permanent contact with senior political officials, with ministers and with senior military chiefs," Rodriguez said.

However the blasts caused "some wounds for seven service personnel" in the National Guard. They were being treated in hospital, he said.

- Iron-fisted rule -

The parade Maduro attended was to mark the one-year anniversary of the Constitutional Assembly, a legislative body packed with Maduro loyalists that arrogated powers from the opposition-ruled National Assembly.

Maduro has remained in power over Venezuela, a major oil exporting nation, despite a collapsing economy and a long-running political crisis that has seen his country isolated internationally.

Hundreds of thousands of Venezuelans have fled the country, where food and medicine are in very short supply, and where inflation this year could reach as high as one million percent according to the International Monetary Fund.

Maduro, a 55-year-old Socialist leader who took over from his late mentor Hugo Chavez in 2013, has effectively sidelined the fractured opposition through control of the courts and the electoral body -- and undinting support from the military, which holds key posts in his government.

Maduro often accuses the opposition and the United States of working together to foment a "coup" to topple him.

He says the economic malaise gripping Venezuela is an "economic war" and any unrest is plotted by foreign powers.

A year ago, four months of street protests flared against his authority that were put down by robust action from the army, the National Guard and police, resulting in 125 people killed.

One of the key reasons for the protests was the creation of the Constitutional Assembly, which aimed to short-circuit the National Assembly in which the opposition won a supermajority in 2015 elections.

Last year, the president said the new body replaced the elected legislature.

The Supreme Court declared the National Assembly dissolved. Although it continues to operate, its decisions are routinely annulled.

The United States and other countries have expressed alarm at the loyalist structure propping up Maduro, saying Venezuelan democracy was being undermined.

Maduro this year brought forward presidential elections that -- after they were boycotted by the opposition and key opposition figures were declared ineligible to run -- handed him a new six-year term.