Brazilian senators flew into Venezuela on Thursday to try to meet with jailed opposition leaders, but they barely made it past the airport, leading Brazil's government to complain about hostile acts against its lawmakers.

The group, which was led by Brazilian opposition leader and former presidential candidate Aecio Neves, landed at a coastal airport but turned back before reaching Caracas, blaming road congestion and a demonstration by supporters of Venezuela's socialist government. The drive usually takes an hour.

Venezuelan hardline opposition leader Maria Corina Machado, who met the delegation at the airport, said maintenance work snarled traffic and the protesters held up the lawmakers' bus. She said dozens of protesters surrounded the bus, shouting insults at the lawmakers and beating on the vehicle, though without damaging it.

The senators wanted to visit high-profile imprisoned Venezuelan politicians, including former mayor Leopoldo Lopez, who has been on a hunger strike for nearly a month.

Neves expressed his extreme displeasure before boarding a plane back to Brazil.

"We're here to show that we are worried, and to insist that democracy prevails through the region. Unfortunately, we have been attacked and stymied," he said in an interview with local Union Radio.

The Brazilian Foreign Ministry released a statement Thursday night saying hostile acts against its politicians are unacceptable and promising to seek an explanation from Venezuela's government.

"The Brazilian government regrets the incidents that affected this visit to Venezuela," the Foreign Ministry said. "Hostile acts from protesters toward Brazilian lawmakers are unacceptable," it added.

It was not the first time an attempt at a jailhouse visit by international figures touched off a spat in Venezuela. Last week, former Spanish Prime Minister Felipe Gonzalez was unable to meet with Lopez and left the country on a Colombian military plane, earning that country a rebuke from the Venezuelan government.

In May, Venezuela blocked conservative former presidents from Bolivia and Colombia from visiting imprisoned opposition politicians, saying they were trying to give Venezuela condescending human rights classes.