BOGOTA -(AP) -- A commander of Colombia's largest rebel group surrendered and -- flanked by the country's president and top generals Monday -- urged his former comrades-in-arms to do the same.

  Rafael Rojas, who said he was a 20-year veteran of the Revolutionary Armed Forces of Colombia and the commander of the group's 46th Front, was the highest-ranking member of the rebel army to turn himself in, authorities said. His surrender Friday was reportedly mediated by a Roman Catholic priest.

  President Alvaro Uribe on Monday introduced Rojas at a nationally televised news conference at a military base in the coastal city of Cartagena.

  Rojas urged other members of the 16,000-strong FARC -- as the rebel group is known -- to also surrender, saying the nearly four-decade war has brought only ruin to this South American country.

  ''Positive things have not resulted,'' said Rojas, who has gone by the nom de guerre Fidel Romero. ``On the contrary, the prolonged war has left only desolation and destruction.''

  Rebels who desert the FARC and other guerrilla armies are put up in protected housing and given the opportunity to change their identities. They also have access to healthcare, education and work training under the government program.

  Uribe, a hard-liner who has stepped up the war against the rebels in his seven months in office, said other rebels should also surrender or face annihilation. ''The decision is to finish with the terrorist problem,'' Uribe said.

  The 46th Front operates in the northern state of Santander, with an estimated 250 troops.

  Some 3,500 people are killed every year in the fighting among rebels, illegal right-wing militias and the government. The Human Rights and Displacement Consultancy, CODHES, which released its annual report on Monday, said more than 412,500 people fled their homes last year because of the violence.