Internet connectivity was gradually restored to San Cristobal, capital of the western border state of Tachira, on Friday morning after an outage of more than 30 hours that also affected smartphones.
Soldiers patrolled the streets after another night in which police firing tear gas broke up protests just as they had the night before, when Internet service was cut. A local TV journalist, Beatriz Font, reported hearing gunshots.
"It's an abuse!" Jeffrey Guerrero, a flour wholesaler, complained just before service was restored. "We've had to find out what's happening in our city from others." He held up his iPhone to show how his Twitter service had halted.
The current wave of anti-government demonstrations, the fiercest unrest since President Hugo Chavez died last March, began in early February in San Cristobal, home to one private and three public universities.
On Thursday night, the U.S. company Zello told The Associated Press that Venezuela's state-run telecoms company, CANTV, had just blocked access to the push-to-talk "walkie-talkie" app for smartphones and computers that has been a hugely popular organizing tool for protesters from Egypt to Ukraine.
Zello supports up to 600 users on a single channel, and company CEO Bill Moore said it became the No. 1 app in Ukraine on Thursday for both the iOS and Android operating systems. In just one day this week, Zello reported more than 150,000 downloads in Venezuela.
Venezuela's information war escalated last week as the government blocked images on Twitter after violence in Caracas claimed three lives amid protests over woes including rampant inflation, food shortages and one of the world's highest murder rates.
The socialist government cemented its near-monopoly on broadcast media during Chavez's 14-year rule, and social media have been crucial for young opposition activists as they organize and exchange information on deaths, injuries and arrests.
Net-savvy activists also reported a serious nationwide degradation Thursday in Internet service provided by CANTV, which handles about 90 percent of the country's traffic.
They said websites including NTN24.com, run by the eponymous Colombia-based regional news network, and online pastebin.com bulletin boards that cyberactivists use to anonymously share information were being blocked.
President Nicolas Maduro ordered NTN24 removed from the air last week after it broadcast video of a student killed by a gunshot to the head in Caracas.
U.S.-based company Renesys, a top analyzer of global Internet traffic, confirmed the website blocking and service degradation, but said it could not determine if CANTV was decreasing bandwidth.
"I certainly don't know from our data if it is deliberate, although given the context, it seems plausible," said Renesys researcher Doug Madory.
Venezuela's traffic to its close ally Cuba over the ALBA-1 undersea cable, meanwhile, appeared unaffected, he said.
Programmer and cyberactivist Jose Luis Rivas, who is from San Cristobal but did not give his location fearing persecution, said the Internet went out in most of the city of 600,000 about midnight Wednesday.
Since protests accelerated last week, activists have posted YouTube videos of riot police and National Guard breaking up demonstrations. Sometimes, the security forces are accompanied by pistol-packing motorcycle gangs of Chavista loyalists that the opposition also blames for killings and other abuses.
Rivas said that on Wednesday night, before the Internet went out in San Cristobal, people were live-streaming video of a crackdown by security forces.
Cutting the Internet deprived people of their only access to uncensored information and Rivas said people told him "they felt fear because they were no longer informed."
Government officials have not commented on the Internet outage and did not respond to Associated Press queries on either it or the service degradation and website blocking.
Spokespeople for Conatel, the government telecommunications regulator, and the Ministry of Information said they were not authorized to discuss the matter.
Conatel's director, William Castillo, tweeted Thursday that social networks were being "invaded by cybercriminals who are attacking accounts and manipulating information."
Information Minister Delcy Rodriguez used Twitter to complain that the networks were being used to incite "coup-directed violence and create anguish."
Hacktivists also have been attacking government websites from abroad, rendering many unreachable with denial-of-service attacks, or data-packet floods.
Images, meanwhile, were visible again on Twitter after last week's outage. Company spokesman Nu Wexler said Thursday that measures which he did not specify were taken to "ensure continuity of service." Twitter also continued to tweet a workaround that lets users in Venezuela receive tweets on their cellphones via text message.
Even before the latest round of protests, Venezuela had been blocking websites that track the black market rate for the country's currency and for several weeks knocked out access to the popular Web address-shortening application Bitly, which was being used to get around online controls.
Venezuelans who want to reach such sites are increasingly using proxy services, which have long been employed by people in China and Iran to circumvent government censors.
The international director of the Electronic Frontier Foundation, Danny O'Brien, said he thought Venezuelan net censorship has been "somewhat haphazard and arbitrary."
Nearly half Venezuela's population relies on government-controlled media as their sole information source, the rest on the Internet.
But cutting off Internet is not smart political strategy, said O'Brien.
"I think the important lesson people should learn from these Internet blackouts is that they just throw fuel on the flames of civil unrest."