GUATEMALA CITY: Authorities in Guatemala arrested seven suspects Friday, including five police officers, in the killing of a prominent lawyer who accused President Alvaro Colom of involvement in his death in a posthumously released video.

The arrests were announced by a special investigation group known as the International Commission Against Impunity in Guatemala, which was invited by the government to probe the May 10 murder of lawyer Rodrigo Rosenberg.

"The result (of the investigation) is not a product of the imagination, nor a matter of leaks or witnesses, because we don't have a single witness," said Carlos Castrensana, a Spaniard who is head of the commission. "But it is unquestionable because it is accompanied by overwhelming scientific evidence."

The five officers arrested Friday are members of the national police force. The other two suspects are an ex-police officer and a former soldier. Castrensana said investigators identified the suspects through security camera footage showing a vehicle believed to contain Rosenberg's killers.

The commission said another set of suspects planned and ordered the killing, but it did not release their names or a possible motive to avoid compromising the investigation.

In a video that surfaced after the murder, Rosenberg is seen looking into the camera and saying, "If you are watching this message, it is because I was assassinated by President Alvaro Colom."

Rosenberg, a 47-year-old corporate lawyer with degrees from Harvard and Cambridge who served as assistant dean at a private university, claimed Colom's government was linked to a corruption scandal at a government bank and said any attack on him would be an attempt to cover that up.

His accusations were distributed to reporters on DVDs at his May 11 funeral and immediately set an already polarized country into a frenzy of protests, allegations of corruption and calls for Colom's resignation.

The president denied any involvement, and his government has suggested that criminal or political interests were behind the video.

"The interior minister informed me that (the suspects were) a well-organized gang that had been operating for some time," Colom said Friday after the arrests were announced. He expressed confidence that investigators would get to the bottom of the case.

Rosenberg's death became a rallying cry for members of Guatemala's dominant elite, many of whom are angry over Colom's attempts to eliminate tax loopholes for corporations and criticize his inability to reduce high rates of violent crime. Tens of thousands of upper-class Guatemalans often flanked by their bodyguards marched in the capital to demand Colom step down.

Colom is overwhelmingly backed by Guatemala's mostly Mayan Indian poor for his efforts to tax the rich and build schools and clinics for disadvantaged communities.