An armed man took an employee hostage at a hotel in the Brazilian capital Monday and forced him to don a vest apparently stuffed with explosives, authorities said.

The gunman called a hotel courier in the early hours, and pushed him into a room on the 13th floor, a police spokesman told Agence France-Presse.

While Brazil's financial sector would like to see social democrat Aecio Neves as president, voters are less keen and opinion polls give the senator and former state governor little hope.

Former congressman Neves, the grandson of a former president, is scion of a political dynasty stretching back decades, but recent polls put him 22 points behind left-wing incumbent Dilma Rousseff.

Brazil's first female president, Dilma Rousseff, is seeking a second term next Sunday, the next step on a political journey that began when she was a Marxist guerrilla tortured under the military dictatorship.

Rousseff, the 66-year-old daughter of a Bulgarian immigrant businessman, was the handpicked successor of two-term predecessor Luiz Inacio Lula da Silva, her Workers Party mentor.

As the battle for Brazil's presidency heats up, the leading candidates -- determined not to scare voters away -- are steering clear of divisive social issues such as gay marriage and abortion.

Incumbent Dilma Rousseff and her top rival Marina Silva are locked in a tight race, with opinion polls showing Rousseff leading in the October 5 first round, but a virtual dead heat in the expected October 26 run-off.

Brazil’s authorities on Tuesday reported the first domestically contracted cases of the mosquito-borne chikungunya virus, prompting the government to announce it was stepping up attempts to control the disease.

The joint disease, which causes high fever and painful arthritis, is endemic to Africa and south Asia but has been moving north as well as west.

Former Brazilian president Luiz Inacio Lula da Silva on Monday rallied behind successor Dilma Rousseff as she battles to stay in power at next month's election amid a corruption scandal and a weak economy.

Lula was mobbed at a rally in central Rio as he made a vociferous defense of Rousseff, who is running neck and neck with environmentalist opponent Marina Silva ahead of October 5 polls.

Brazilian President Dilma Rousseff has insisted a corruption scandal at state oil giant Petrobras does not involve her government, as she fends off a new threat to her re-election bid.

"I think this does not place the government under any suspicion, as nobody in the government has been officially accused of anything," Rousseff said in comments made Sunday and carried by newspapers on Monday.

Brazilian President Dilma Rousseff, chasing re-election on October 5, is keeping her Workers Party (PT) seat warm for predecessor Luiz Inacio Lula da Silva to return in 2018, the party chairman said Saturday.

Inmates rioting for better facilities in a Brazilian jail killed four fellow prisoners, decapitating two of them, and took two guards hostage, officials said Sunday.

The uprising took place in the Cascavel state correctional center in the southern city of Parana that currently holds 1,140 inmates, according to Elson Faxina, a state judicial spokesman.

A 40-year-old Lebanese expatriate was killed in Brazil by an unknown assailant as he was heading to his work, media reports said on Sunday.

According to Voice of Lebanon radio (93.3), Ramzi Jaber, who hails from the southern village of Mhaibib in the town of Marjeyoun, was killed by an unknown assailant on the Ponte de Amizade bridge, which connects the Brazilian city of Foz do Iguaçu and the Paraguayan city of Ciudad del Este.