MOSCOW (AFP) - Russia's parliament passed a bill on Friday requiring Internet companies to store Russians' personal data inside the country in an apparent move to pressure sites such as Facebook and Twitter into handing over user data.

Introducing the bill to parliament this week, MP Vadim Dengin said "most Russians don't want their data to leave Russia for the United States, where it can be hacked and given to criminals."

"Our entire lives are stored over there," he said, adding that companies should build data centres in Russia.

But the bill would also increase pressure on social networking services which do not have offices in Russia and have become a vital resource for anti-government groups.

Both Facebook and Twitter refuse to hand over user data to governments.

Just three days before the bill was formally proposed last month, Twitter's public policy chief Colin Crowell visited Russia to speak with media watchdog Roskomnadzor. Few details of the visit were publicised, but access to user data is thought to have been top of the list.

Russia is also asking Twitter to open a local office, which the company has so far refused to do.

The new bill would not come into force until September 2016 but would potentially provide the government with grounds to block sites that do not comply.

That could cause major problems for Russian companies, such as airlines that rely on foreign-based online booking service.

Hastily passed by the Duma, where it was only introduced in late June, the bill must still be approved by the upper chamber and President Vladimir Putin before it becomes law.

"Nobody wants to relocate to Russia, but I am pessimistic. I think (the Russian authorities) will make them relocate the servers," said Mr Andrei Soldatov, a journalist who tracks Russia's security services.

"For the most part, this is directed against Gmail, Facebook, and Twitter," he said.

Google and Yandex, its Russian equivalent, told AFP they need time to study the final version of the law before commenting.