Story highlights Maria Corina Machado tweets she is not afraid and will return to the neighborhood

A couple on a motorcycle fire at Machado's bus, a spokesman says

No one is injured, says the spokesman from the candidate's campaign

Machado is one of several vying to be an opposition unity candidate, running against Chavez

A couple on a motorcycle fired shots into a bus carrying Venezuelan opposition presidential candidate Maria Corina Machado and her supporters Saturday, a campaign spokesman told CNN en Español.

No one was injured in the incident, which happened on the east side of the capital, Caracas, according to Alfredo Mesa from Machado's campaign.

The El Nacional newspaper published a photo of what it said was the shooting, which showed two people on a motorcycle. Wearing a red T-shirt, the man on the back is pointing a gun at a bus.

Machado is one of several presidential candidates who will participate in a primary in February. The winner will be the unity opposition candidate to run against President Hugo Chavez.

On her official Twitter page, Machado wrote after the incident she is not afraid and that she will return to the neighborhood.

"Those responsible for this violence are small groups, but armed, and do not represent the democratic values of the 23E," she wrote, referring to the area where the shooting happened.