Venezuelan President Hugo Chavez's main rival in an upcoming election was attacked with firearms and stones, Venezuelan television reported.
Manuel Rosales and his team were ambushed Thursday in a poor area of Caracas by alleged Chavez supporters who threw stones and bottles at them, the private television channel Globovision reported.
Later unknown attackers further up the hill exchanged shots with Rosales' guards in the area known as Boqueron in western Caracas, the report said.
Preliminary reports said no one was seriously injured in the attacks. Elections are set for December 3.
Globovision showed footage in which a group clearly identified as Chavez supporters attacked Rosales' group and journalists present.
The attackers apparently tried to prevent him from entering an allegedly pro-Chavez area.
Opposition official Carlos Melo confirmed Globovision's report, and said Rosales managed to finish his scheduled tour of the Magallanes Hospital in the area.
Rosales later left the area amid further attacks from people who wore clothes and other symbols that linked them to Chavez.
Melo told Union Radio that the attackers fired about 15 shots on Rosales' entourage, and that a "clearly pro-government" group threw stones when Rosales was visiting the hospital.
The local police used gas to disperse the demonstration, he said.
Rosales blamed an ambush earlier this week also on the current Venezuelan president.
"I want to tell Venezuela that if anything happens to me, if I am killed in those ambushes that I am being the object of, it is on Chavez orders, and I hold Chavez responsible.
And the people will know what to do if anything happens to me, if I am murdered," the candidate said.
Rosales said he is not afraid and added if he is killed Venezuelans "will go out on the streets and bring down the government".