Mozambican police stormed an office of the Renamo opposition on Wednesday, reportedly arresting 15 people and using teargas to disperse a crowd.
"Police arrested 15 Renamo members who were trying to campaign" in the centre of the country, Radio Mozambique reported.
The incident occurred amid renewed tension between the Frelimo-led government and its former civil war foes, who are threatening to disrupt local elections set for November.
"Our force dispersed... armed men who were gathered at the Renamo offices and were constructing wooden structures and tents," said police spokesman for Sofala province, Matheus Mazive.
"They used tear gas because these individuals resisted."
Renamo insisted its members were unarmed and did nothing to provoke an attack.
"Police came to attack our offices where our demobilised soldiers were, civilians who were not armed at any moment and who never caused any disturbance in the area, " Renamo's Secretary General, Manuel Bissopo told AFP.
In a similar incident in March 2012, police raided Renamo's headquarters in the northern Nampula province, killing two after a group of around 300 men had set up a makeshift camp.
Bissopo denied allegations Renamo ex-fighters were setting up bases across the country.
"It is not a base," he insisted adding " throughout the country, the demobilised soldiers decided to come to our offices because they are being persecuted at home."
"The veterans who fought the sixteen year war are not satisfied with what has happened over the last twenty years."
Late last year Renamo's president, Afonso Dhlakama set up a bush camp in the Gorongosa mountains in Sofala where he began retraining former guerilla fighters.
He threatened a return to war unless government met his demands for a renegotiation of the terms of the 1992 Rome Peace accord signed between Frelimo and Renamo.
However, after two meetings between government and the opposition group, the issue died down.
Renamo is now threatening to disrupt municipal elections set for November after changes it proposed in the electoral law were not accepted.
"The veterans' intention is that more elections don't happen. We don't want elections that will just confirm Frelimo's fraud? We can't go on under a group of criminals," Bissopo said.
The government appears to have hardened its position in the face of Renamo's threats.
"If Renamo continues to overstep the line, we will have no alternative but to take measures to guarantee calm and public order," said Deputy Interior Minister Jose Mandra independent daily, "O Pais" reported on Wednesday.