Multimillionaire businessman Horacio Cartes has been sworn in as the president of Paraguay in a ceremony in the capital, Asuncion, the BBC reported.

Cartes, a relative newcomer to politics who had not voted before 2008, was elected in April with 45.8 percent of the vote. He defeated his closest rival, Liberal Party candidate Efrain Alegre, by nine percentage points.

Cartes, whose term runs through August 2018, built a family fortune with firms that dominate industries including tobacco, banking, soft drinks and soccer.

But he has also faced allegations that his wealth was obtained through drug trafficking and money laundering. A State Department cable published by Wikileaks accused Cartes of heading a drug-trafficking and money-laundering operation, and he is said to have been under investigation by the Drug Enforcement Administration, Fox News Latino reported.

In his inaugural speech, Cartes, leader of the center-right Colorado Party, promised to wage war on poverty in Paraguay, one of the poorest countries in South America.

"I'm not in politics to make a career of it or become wealthier," he said. "I'm in politics to serve my people, improve the future of new generations and treasure our identity as a free, independent and sovereign people."

He also promised to "put the fatherland first" and to "create opportunities for all" to combat Paraguay's rampant inequality.

Cartes had campaigned on a platform of poverty reduction and job creation.

Choosing his cabinet, he broke with the established tradition of naming senior party members to key posts, instead choosing technocrats and business people.

His Colorado Party was in power for 60 years and played a key part in supporting the military rule of Gen Alfredo Stroessner from 1954 to 1989.

In 2008, it was beaten by a left-wing coalition headed by Fernando Lugo. Last year President Lugo was impeached by Congress over his handling of a land eviction in which 17 people died. The impeachment process took less than 48 hours and was deemed unfair by many of Paraguay's neighbours, leading to the country's exclusion from the Mercosur trading bloc.

The presidents of the Mercosur countries (Argentina, Brazil, Uruguay and Venezuela) said in July they would lift Paraguay’s suspension after Cartes' inauguration. Paraguay has said it would not return to the Mercosur fold as long as Venezuela held its rotating presidency.

Paraguay has objected to Venezuela's inclusion in the trading bloc.

Asuncion says that a new member can only be included after a unanimous vote and argues that such a vote should not have been held while Paraguay was suspended.

Venezuelan President Nicolas Maduro was not invited to Cartes' inauguration. Caracas will hold Mercosur's rotating presidency until July 2014.