The shootings happened two days after Renamo information chief Jeronimo Malagueta said the party would “paralyse” roads and a railway link vital to coal exports.
Police detained him in the early hours of Friday, shortly before the attacks.
The former rebel group ended a 16-year-long guerrilla war in 1992.
But fears that its peace accord with the governing Frelimo party could collapse grew late last year, when Renamo leader Alfonso Dhlakama returned to his bush camp in the Gorongosa mountains in central Mozambique.
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One of our tyres was hit by a bullet and it burst, immobilising the vehicle”
Monica MalotePassenger
‘Renamo encircled’
On Monday, six soldiers were killed when gunmen attacked an armoury in the central region of Dondo; a large number of weapons were stolen.
Renamo denied it carried out the raid.
The party has not commented on the latest attacks, but its adviser Rahil Khan confirmed that Mr Malagueta had been detained in the capital, Maputo.
“In a short period of time he has been taken to different police premises, including the maximum security jail. This is a bad joke. It’s regrettable,” he said, at a press conference.
“We think that the ruling Frelimo party is behind all this. We don’t know why they are doing this. But for sure this is going to derail the on-going negotiations process between Renamo and the government.”
Interior Ministry spokesman Pedro Cossa said gunmen ambushed vehicles in three attacks in central Sofala province, on the highway linking northern and southern Mozambique.
He said at least two people were killed and five wounded in the attacks.
“I have no doubt that it was Renamo,” Mr Cossa is quoted by Reuters news agency as saying.
The attacks have rekindled memories of the civil war when people were scared to travel and the economy was severely disrupted, reports the BBC’s Jose Tembe from the capital, Maputo.
A wounded commuter, Monica Malote, told state radio that gunmen opened fire on a convoy of cars travelling between the towns of Machanga and Muxungue.
“The first cars passed the area without problems. But as we were moving to Muxungue gunmen started shooting at our vehicle. One of our tyres was hit by a bullet and it burst, immobilising the vehicle,” she said.
“We hurriedly fled into the bush. But before I got there I was severely injured by one of the bullets.”
Police have detained Mr Malagueta for questioning and he has not yet been charged, our reporter says.
State radio said rapid-response police units had started patrolling the main north-south highway.
On Wednesday, Mr Malagueta said Renamo planned to carry out attacks because Mr Dhlakama was under threat from government forces.
“Renamo will position itself to stop the circulation of vehicles transporting people and goods, because the government uses these vehicles to transport arms and plain clothed soldiers,” he said.
“The government doesn’t give us any other option. Renamo is encircled. We are going to lose our leader,” Mr Malagueta added.
‘Ignored’
He also warned that Renamo would target a rail link to Mozambique’s Beira port.
The link is used mostly by Brazil’s Vale and London-listed Rio Tinto, which are among companies developing Mozambique’s coal deposits and offshore gas fields, according to Reuters.
Mozambique has been been trying to rebuild its economy since the brutal civil war ended in 1992.
A force of about 300 Renamo men have remained armed since the accord, despite efforts to integrate them into the army or police force.
Mr Dhlakama says he needs his own personal bodyguards, and the men usually stay in his bush camp in the Gorongosa mountains.
After the civil war ended, Mr Dhlakama moved out of the camp to live in Maputo and later in the northern Nampula province
But he returned to the mountains last year, saying he needed to be close to his men who had felt ignored.
In April, Renamo said it carried out an attack on a police post in the central Dondo region.
Mozambique is due to hold local elections in November, and presidential and parliamentary elections next year.
Renamo and Frelimo have so far deadlocked in talks aimed at resolving differences over the polls.
Renamo is demanding changes to the electoral commission, alleging it is biased in favour of Frelimo.
Frelimo has governed Mozambique since independence from Portugal in 1975.
Renamo, which was formed around the same time, was backed by white rulers who were then in power in neighbouring South Africa and what is now Zimbabwe.