Google has unveiled two new mid-range versions of its Pixel smartphones as the technology giant attempts to broaden its appeal.

The company will sell the new Pixel 3a starting at €350 and the Pixel 3a XL for €450 - several hundred euro cheaper than current generation flagship phones.

The technology giant said it has used "software optimisations" to ensure many of the key features from its  flagship Pixel 3 also appeared in the 3a.

Announced at the company's annual developer conference, Google I/O, the technology firm said the aim of the new devices was to "bring premium features at a price people will love".

Recent research has suggested smartphone users are upgrading less frequently, partly because of rising prices.

The tech giant also demonstrated a string of updates to its other products, including new camera features in search results, such as the ability to see 3D models for some image searches.

The feature will also enable users to use augmented reality to place 3D models into their own space through their phone's camera and see a digital version of the object to scale in the real world.

A new version of Google Duplex, the controversial artificial intelligence software that can make phone calls on behalf of humans, was also showcased.

The technology received a mixed reaction when first introduced at the event last year, with some analysts expressing unease at a robotics programme pretending to be human - which forced Google to clarify the software would always disclose what it was at the start of a call.

The latest version showed Duplex being used as an assistant on the web - booking a hire car automatically when prompted using voice commands and gathering relevant information from apps as needed.

Google chief executive Sundar Pichai said the range of updates were part of the firm's mission to "organise the world's information and make it universally accessible".

He added the company's products would be built "on a foundation of user trust and privacy" and would share a single goal "to be helpful".

"We want to build a more helpful Google for everyone," he said.

"It is our responsibility to create things that improve people's lives."

The developer conference in California was also used to offer a preview of the next version of the Android mobile operating system, the world's most commonly used smartphone software.

Known only as Android Q, it will include new features such as digital well-being tools, including a Focus Mode that will enable users to disable apps they find distracting.

It will be joined by extended parental controls that will enable them to remotely approve app downloads by their children as well as set time limits for specific apps.

Technology companies have come under increased pressure to respond to concerns from researchers and charities over the impact of their devices on society, with many calling for smartphone addiction to be classed as a disease.

Companies including Google and Apple have since begun introducing health and well-being tools to help users more easily step away from their devices.

The keynote presentation was also used to announce a merger of Google's Home products with Nest - the smart home security firm the company owns.

The screen-based smart home device Home Hub has been rebranded Nest Hub and a new Nest Hub Max, with a larger 10-inch screen and a built-in camera, was also announced.