Young babysitters who use listings to find jobs are being warned after police received multiple complaints about a man making indecent phone calls.

The calls have targeted girls between the ages of 11 and 16 and come from a blocked number, Calgary police said in a press release on Thursday.

The girls are typically engaged in conversation that grows increasingly graphic, police said.

Acting Insp. Steve Lorne told CBC News that police have received around 10 complaints since late 2019.

'Parent doesn't know until there's a reaction'

Lorne said that in a few instances, parents have initially picked up the phone calls — and unwittingly handed the phone to their children after the caller inquired about the babysitter listings.

"The conversations occur in the presence of the parent, and it's not on speaker," Lorne said.

"So the parent doesn't know until there's a reaction within the child. And then they'll go, 'What is going on here?'"

He emphasized the importance of parents and children reporting these incidents.

Lorne used to be the provincial co-ordinator for the child Internet exploitation unit, and he said he fears the caller will attempt to "groom" children and escalate contact.

"It can lead to where he'll schedule a meeting with the children," Lorne said.

Here's some tips to safeguard sitters

Tayah Klassen, the child and family coordinator at the Brookfield Residential YMCA, runs the facility's babysitting course.

She says it features a full chapter on online safety and includes tips for parents on keeping their children secure.

"It's not like it used to be in babysitting," Klassen says.

"I'd post my resume with my phone number on a bulletin board at the grocery store. And now, unfortunately, we live in a different world where that's not so safe anymore."

The course, Klassen said, encourages kids to speak up if they get "a bad vibe" from a family.

Tayah Klassen runs the babysitting program at the Brookfield Residential YMCA at Seton. She offered a number of tips for babysitters and their parents to stay safe. (Helen Pike/CBC News)

Parents are also advised to do a phone interview — followed by an in-person meeting — with families they don't know before allowing their children to babysit for them.

And even then, Klassen said, she recommends that parents know the families from their personal networks beforehand.

"Unless they are from your own community, I would still be wary about it," Klassen said.

When it comes to posting online, she says babysitters and parents should beware.

"It's so vital not to ever post your information online. And when it comes to your kids, you never want to post their information online either."

Police suggest these measures

The release from police also included tips for "thoughtful Internet practices" that parents can use to help decrease the likelihood of an indecent phone call:

Do not include a photograph of a babysitter on any website.

Do not answer any phone calls from blocked or private numbers.

Do not include the babysitter's phone number on websites; police recommend communicating via email initially.

Make sure a parent or guardian is present and listening when the babysitter is communicating with the person looking to hire them.

Never let a babysitter meet the individual hiring them alone.

Calgarians who have any information about the calls — or have received calls themselves — are strongly encouraged to contact police using the non-emergency number, 403-266-1234.