CARACAS (Reuters) - President Nicolas Maduro’s plan to rewrite the constitution is opposed by 85 percent of Venezuelans, according to a survey by polling company Datanalisis carried out as protests calling for presidential elections intensified.

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In the poll, conducted between May 29 and June 4, 85 percent of respondents agreed with the statement: “There is no need to change the current constitution. What the government should do is enforce it.”

Maduro, 54, has called a July 30 election to choose lawmakers who will work on the new charter, calling it a way to restore peace after two months of often violent anti-government unrest that has killed 67 people and injured thousands.

Opposition parties say they will not take part in the vote, which could dissolve the current, opposition-dominated parliament. The proposal has run into rare criticism from within the government’s own ranks.

Critics say the plan is designed purely to keep Maduro in power, with rules skewed in the government’s favor. They want to bring forward the next presidential vote due at the end of 2018.

“Hunger, scarcity and out-of-control violence is not going to be solved with a new constitution,” said Oscar Arnal, an academic at a rally on Saturday in Caracas, where security forces used tear gas and water cannons to clear protesters who blocked a central highway, throwing fireworks and Molotov cocktails.

“All they want is to stay in power for centuries,” said Arnal. Protesters left burning barricades and clashed with security forces in the east and west of the city, while incidents were reported in other regions of the oil-producing nation.

At least three people were injured, according to Reuters witnesses and live TV images, while shoppers in the Orinoco river-side city of Puerto Ordaz were forced to take cover when tear gas shells hit the mall they were in.

German Chancellor Angela Merkel on Friday called the situation in Venezuela “concerning,” in comments the government decried as interference that would fuel opposition violence.

The poll was posted on the website prodavinci.com, which publishes largely anti-government opinions, and confirmed by Datanalisis’ head Luis Vicente Leon, who has been a critic of President Nicolas Maduro.

Datanalisis did not reveal the number of participants, saying interviews were done by telephone with families from a range of economic backgrounds.

Maduro’s approval rating in the poll was 21.9 percent, including people who considered his performance as president, not bad, good and very good.