(Adds Santos and Zuluaga comments)
By Peter Murphy
BOGOTA, May 6 (Reuters) - Colombia said on Tuesday it had uncovered spying aimed at disrupting peace talks with leftist rebels that might have included hacking the e-mail of President Juan Manuel Santos after the government raided an office used by an opposition political candidate's staff.
Colombia's prosecution service raided an office used by right-wing presidential candidate Oscar Ivan Zuluaga's social media team in an up-market area of northern Bogota on Monday after receiving a tip-off, the government said.
One man was arrested and is being questioned in the incident that came just three weeks before a presidential contest in which Santos is favored to win re-election.
"The purpose of this office, the aim of the people linked to this criminal enterprise was to sabotage, interfere with and affect the peace process in Havana," Attorney General Eduardo Montealegre told reporters.
There were "initial indications" that Santos' emails were being monitored from the facility, he added.
Zuluaga's team acknowledged the office was used by a publicity team that worked to promote the candidate on social media and aided with data protection.
"Of course, we condemn any illegal activity, if proven, which took place there and await the swift results of the investigation and the maximum sentence for those responsible," Zuluaga's campaign said in a statement.
"The campaign cannot be associated in any way with illegal activity ... We express our huge surprise that an illegal act was committed in the offices from which the services were received."
Zuluaga, speaking later on television, said he was suspicious of the timing of the discovery, coming a day after a Santos campaign advisor quit amid allegations he had received a $12 million bribe to help suspected drug traffickers avoid extradition to the United States.
The adviser, Venezuelan political guru JJ Rendon, denies receiving any sum.
A statement from the prosecutor's office said information so far revealed the spying targeted a member of the FARC rebels in charge of media relations in Havana, where peace talks have been conducted, and the email accounts of two Cuban journalists.
"It is very, very serious that any person or any organization is deliberately trying to sabotage the peace process through illegal interceptions," said Santos.
"I'm going to ask the prosecutor to please get to the bottom of this matter."
President Santos has made the Havana peace talks the hallmark of his four years in office, and he says he needs to secure a second mandate on May 25 to reach a peace deal ending five decades of civil conflict.
Santos is the front-runner in the elections that look headed for a second round of voting. His opponent Zuluaga has been critical of the peace process because it could lead to immunity or light sentences for the rebels.
The conflict grew out of a struggle over land reform, but the government says the FARC rebels and a smaller rebel group, the ELN, have for years been involved in trafficking cocaine.
The latest spying accusation follows an incident in February when rogue members of the military were accused of intercepting text messages from government negotiators holding confidential talks with FARC rebels in Cuba.
A preliminary military investigation concluded no spying took place. The prosecutor's office and the military are investigating separately.
(Additional reporting and editing by Julia Symmes Cobb; Editing by Cynthia Osterman)