Two Ottawa residents are in custody on terrorism offences and more arrests are expected in the coming days in what police sources are calling a major investigation into a terror plot targeting Canada. One of the suspects is reportedly linked to al Qaeda.

RCMP provided no details on the identity of the accused. However, sources told CTV News the suspects are wanted for an apparent bomb plot still in the planning stages.

The arrests were reportedly made Wednesday because one of the accused was preparing to travel overseas.

Sources told CTV News the case is regarded as a significant anti-terrorism operation that CSIS and the RCMP have been working on for about one year. The House of Commons was not considered a target.

RCMP haven't elaborated on the nature of the allegations, except to say they are terror-related. Sources say the case is similar to the Toronto 18, a group of Canadian citizens who were charged with planning terror attacks in Canada.

Two west-end homes raided

The arrests in Ottawa come as RCMP raided two west-end homes Wednesday, which remained under heavy police presence for most of the day.

Police raided a townhouse on Esterlawn Private in a quiet neighbourhood in the Carlingwood area at about 6:30 a.m.

Neighbours say a devout Muslim couple who kept to themselves live in the townhouse with their baby.

"It's pretty scary – scared to be in a quiet neighbourhood and hear that next door," said Janice Vurtt, who lives two doors down.

No suspicious activity, say neighbours

Another neighbour who lives next door told CTV Ottawa she often heard the couple chanting in prayer.

"That's the only thing I've ever heard," said the woman, who would only identify herself as Louise.

She said the couple moved to the neighbourhood about one year ago and were generally good neighbours. She added they appeared to be between 35 and 40 years old.

Although friends often visited the house, she said she never noticed anything suspicious.

Vurtt – who's lived in the neighbourhood for 17 years – said two other adults may have also lived in the townhouse.

Gathering evidence

Investigators spent most of the morning removing computer equipment from the home. They also spent lots of time taking photos of a car, which was later towed away.

RCMP also raided a highrise on Woodridge Crescent in the Bayshore area, where investigators were seen entering the building with cardboard boxes around the noon hour.

Investigators are currently searching the homes for additional evidence. Police have not released any other information.

Public Safety Minister Vic Toews has not said anything about the case. However, he released a statement Wednesday saying the government continues to be vigilant about monitoring any threats against Canada.

RCMP will hold a press conference Thursday afternoon to reveal more details about their investigation.