Google has started uploading the latest version of its Android system to users' smartphones.

Owners of the HSPA+ version of Samsung's Galaxy Nexus - available in the UK, most of Europe and the US - are the first to receive the update.

Google says the Jelly Bean software offers an improved search experience.

But it does not appear to have amended the system to take account of a patent row that briefly caused the Nexus phone to be banned from sale in the US.

The update - also known as Android 4.1 - poses a direct challenge to Apple's voice-controlled "assistant" Siri.

Automatic searches

Google says it has improved Voice Search so that it can display answers to spoken questions from sources including Wikipedia, the CIA World Factbook and Freebase - a community-run knowledge database.

It has also introduced Google Now which is designed to offer information without the user having to actively trigger a query.

"Google Now tells you today's weather before you start your day, how much traffic to expect before you leave for work, or your favourite team's score as they're playing," said the firm in an update to the Nexus page on its Google+ social network.

Both features are potentially in breach of an integrated search patentfiled by Apple.