Brazen thieves in Melbourne's CBD are stealing people's mobile phones right out of their hands, often while they are texting, Victoria Police say.

The victims are often tourists and young people.

Detective Acting Sergeant Adrian Smith said when people are solely focused on their phone their awareness levels of what is going on around them drops and thieves "are really capitalising on that".

"We're seeing a lot of people having phones plucked from their hands while they're simply texting or browsing social media," Detective Acting Sergeant Smith said.

"By the time people realise their phone is missing the offender is long gone."

Police said they were also seeing instances of targeted pick-pocketing.

They have advised people to be conscious of keeping their phones safe.

"We'd ideally like people to keep their valuables out of sight when in public, but we understand that's not always feasible," Detective Acting Sergeant Smith said.

"Make sure you remain aware of your surroundings and return it [the phone] to a safe place, like a zipped up bag s soon as you can."