GUATEMALA CITY (AP) — Guatemalan ex-President Alvaro Colom is defending his actions in a case of suspected corruption involving bus concessions.

Colom has told a judge that upgrading the public transit system was a legitimate measure to prevent deadly attacks on drivers and passengers.

Colom argued Wednesday that the attacks on drivers "were planned to destabilize my government." The case centers on 25-year concessions for Guatemala City bus routes. The private companies that won the contracts were later exempted from taxes.

Prosecutors say the process was deeply flawed, and it is suspected that the government was defrauded out of millions of dollars.

The judge will decide whether the case proceeds against Colom and 12 former Cabinet ministers, including the current president of Oxfam International. They were arrested in mid-February.