WINNIPEG - The last thing Dominic Maryk said to his mom as he hugged her goodbye was, "Don't worry. It's going to be OK."

That was almost a year ago and Emily Cablek hasn't seen her eight-year-old son or his six-year-old sister Abby since. Police say the two children could be anywhere -- even out of the country -- after they disappeared last August during a visit with their father Kevin Maryk.

"It's two pieces of my soul and my heart missing," their 27-year-old mother said Wednesday. "I just want them back."

Police took the rare step of holding a news conference to mark the anniversary of the children's disappearance.

Investigators are calling it a case of parental abduction and are asking people to come forward with information. They say Kevin Maryk is likely with his 20-year-old nephew, Cody McKay. They have issued a warrant for McKay's arrest, on top of the outstanding warrant for Kevin Maryk.

No one has reported McKay missing, but police say he hasn't been seen since the kids disappeared and he was living with Kevin Maryk at the time. Officers say it's rare for children to be gone for this long if they have been taken by a parent, and suspect people know where the youngsters are but aren't sharing that with police.

Cablek directed her plea at McKay on Wednesday, urging him to do the "right thing for Dominic and Abby."

The last year, Cablek said, has been agony.

"Every day is pretty well the same -- wake up and all you want to do is go back to bed," she said as she wiped away tears. "You hope for a phone call. You feel lost. I've felt lost."

Still, she said, she's never going to give up looking for her children.

Police say they haven't given up either. Det. Clyde Raven said they've been approached by the television show "America's Most Wanted" which they hope will raise awareness of the alleged abduction in the United States. They are also posting videos on YouTube in an effort to generate tips.

"This has gone on long enough. It's been a year," Raven said. "It's gotten to a point where it's ridiculous. We need to get these kids back. People know or have information about where these people are. We need that information."

"These children could be anywhere now."

The children aren't likely to be in school and their father is probably not working legally, Raven added.