MONTREAL -- Four Montreal police officers have been arrested, with two facing various charges including perjury, attempting to obstruct justice, soliciting and obtaining sexual services, Chief Philippe Pichet said Thursday.

Faycal Djelidi faces nine charges and David Chartrand four, Pichet told a news conference.

"Unfortunately, police officers committed reprehensible acts and as a police organization we have to intervene and do our job right to the end," he said.

The other officers were not named and no charges were announced against them.

Pichet said the probe began last December after irregularities were noticed with regard to the control of informants.

He said the force tried to address the problems at the administrative level before launching an internal investigation.

"Protecting our sources and our criminal intelligence is crucial and a constant concern for us," he said.

He said nobody was currently in danger due to the officers' actions.

Djelidi and Chartrand are each charged with perjury and obstructing justice, while Djelidi is also charged with breach of trust, soliciting, and obtaining sexual services.

Pichet said he was disappointed by what happened.

"Nobody is above the law and police officers are no exception," he said. "This is a deplorable situation and as police officers we all feel concerned when one of our own crosses the line."

The two officers, who worked as investigators in a multidisciplinary and youth co-ordination unit, have been suspended without pay.