* Pakistan, Ethiopia, Bahrain slide backwards
* Estonia tops United States for No. 1 spot
WASHINGTON, Sept 24 (Reuters) - Government restrictions on the Internet have risen over the past year around the world as regimes use violence against bloggers and turn to censorship and arrest to squelch calls for reform, a new report from a U.S. advocacy group has found.
Pakistan, Bahrain and Ethiopia saw the biggest rollbacks in Internet freedom since January 2011 and were among the 20 countries out of 47 assessed by Freedom House that declined in their rankings.
In contrast Tunisia, Libya and Burma, all countries that have seen dramatic political opening or regime changes, improved over previous years along with 14 other countries, the U.S. group, which advocates democracy and open societies, said.
The report was released the day that Vietnam handed out stiff jail terms to three high-profile bloggers for their bold criticism of government handling of land rights issues and corruption.
Estonia topped the list of countries for freedom of the Internet with the United States in second place, according to the Freedom House report. The rankings were based on obstacles to Internet access, limits on content and violations of user rights.
Estonia has a highly developed online culture that includes online voting and access to electronic medical records and some of the lightest content restrictions in the world, the report found. The United States has fallen behind in Internet speed and cost and broadband availability.
Methods for controlling free speech on digital media also have grown more sophisticated and diverse the past year.
Governments have passed new restrictive laws in 19 states. In Iran, censors have improved software for filtering content and hacked digital certificates. In Pakistan, virtual private networks are banned. And in 14 countries the governments have followed China's lead in hiring armies of commentators to manipulate online discussions, the authors said.
"As authoritarian rulers see that blocked websites and high-profile arrests draw local and international condemnation, they are turning to murkier - but no less dangerous - methods for controlling online conversations," said Sanja Kelly, project director for Freedom on the Net.
Other findings include: * Physical attacks against government critics are intensifying: In 19 of the 47 countries assessed, a blogger or user of information technologies was tortured, disappeared, beaten, or brutally assaulted for their online posts. In five countries, an activist or citizen journalist was killed after posting information that exposed human rights abuses * Bloggers and ordinary users increasingly face arrest for political speech on the web: In 26 of the 47 countries, including several democratic states, at least one blogger or Internet user was arrested for content posted online or sent via text message. * Surveillance has increased with few checks on abuse in 12 of the 47 countries examined * Citizen pushback has increased and had an impact in 23 countries. Advocacy campaigns, mass demonstrations, website blackouts and constitutional court decisions have resulted in censorship plans being shelved, harmful legislation being overturned and jailed activists being released.
The report covered the period from January 2011 to May 2012 and is its third on Internet freedom, based on information from researchers mostly based in the 47 countries.