ASUNCION (Reuters) - Protesters were collecting signatures on Sunday demanding the withdrawal of a proposed amendment that would allow Paraguay’s president to stand for re-election while his allies vowed to move forward with the measure despite Friday’s violent clashes.

The capital has been relatively calm since rioters stormed and set fire to Congress, though anger simmers over the death of a protester who was killed when police fired shots at the headquarters of the country’s second-largest political party.

Paraguay’s constitution, introduced in 1992 after 35 years of dictatorship, strictly limits presidents to a single five-year term. Friday’s secret vote in the Senate on a constitutional amendment that would allow President Horacio Cartes to run for re-election sparked riots.

“The most important thing is to withdraw the amendment ... if this is not done, we are sitting on a time bomb that could blow up at any moment,” said Asuncion Mayor Mario Ferreiro, a member of an opposition party.

Violence flared in Asuncion as 2,000 ministers and businessmen gathered for the Inter-American Development Bank governors’ meetings meant to show Paraguay’s economic potential to the world after years of political stability under Cartes.

The soy and beef exporting nation has become one of South America’s fastest-growing economies in recent years and tax breaks are luring manufacturing investment.

Paraguay’s lower house could vote on re-election as soon as Tuesday, when leaders will set the chamber’s agenda. However, firemen have warned the Congress building may be at risk of collapsing, potentially delaying legislative sessions following Friday’s fire.

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A popular referendum would still be required for the measure to be adopted.

Lawmakers loyal to Cartes want to press on with the amendment, which could also benefit former leftist President Fernando Lugo. Lugo was impeached in 2012 when lawmakers ruled he had failed in his duty to maintain social order following a bloody land eviction in a swift vote that was criticized abroad.

“The amendment project will be debated when the lawmakers consider it pertinent and I am convinced it will be approved,” said Senator Lilian Samaniego, a close ally of Cartes.

Cartes, a soft-drink and tobacco mogul elected to a five-year term in 2013 for the conservative Colorado Party, enjoys a majority in the lower house.

Cartes has appealed for calm in messages on social media.

Some business groups called on the government to abandon the re-election campaign to guarantee order.

“No one should be above the law nor try to modify it during a period of tension,” said an ad from the Federation of Production, Industry and Commerce published in local papers.

A small group of protesters continued to keep guard outside Congress on Sunday.