Renesys Corp., a company that maps the pathways of the Internet, said it could not confirm whether the blackout was government-orchestrated. But the cut recalls a similarly dramatic outage in Egypt, Sudan's neighbor, when authorities shut off Internet access during that country's 2011 uprising.
"It's either a government-directed thing or some very catastrophic technological failure that just happens to coincide with violent riots happening in the city," said senior analyst Doug Madory. He said it was almost a "total blackout.
The New York-based Committee to Protect Journalists said it was alarmed by the reports of what seemed like an official attempt to stifle coverage, and called on the government to restore the country's connection.
A police statement said three people have died in three days of rioting over the lifting of fuel subsidies—two in the town of Wad Medani south of Khartoum, and one in the Omdurman district of the capital.
In northern Khartoum, Sudanese security forces fired tear gas to disperse dozens of protesters who demonstrated and torched a police station.
Wednesday's protests took place in several areas of Kadro district, 15 miles (25 kilometers) from the capital's city center, where protesters blocked roads using lengths of pipe and burning tires.
The riots that began in the state of Gezira, south of Khartoum, have turned into a call for the ouster of President Omar al-Bashir, who has ruled the country for more than two decades. The rioting started after Sudan's government decided to lift subsidies, immediately doubling prices of gasoline and fuel.
The semi-official Sudan Media Center on Wednesday quoted Gezira governor Al-Zubair Bashir Taha as saying that aside from police stations, riots there targeted power and gas stations, banks, shops and private property.
The SMC also quoted the deputy head of the Sudanese parliament, Samiya Ahmed Mohammed, as saying she hopes the "opposition understands the measures with objectivity."
Sudan lost most of its main oil-producing territory when South Sudan broke off as an independent state in 2011.
An initial attempt by the government to cut subsidies sparked similar protests but they were quelled by a heavy crackdown on protesters, activists and journalists.
Al-Bashir is wanted by the International Criminal Court on allegations linked to the conflict in Sudan's western region of Darfur where an estimated 300,000 people have died since 2003 due to fighting between government-backed tribes and rebels.
Al-Bashir received an invitation to attend the U.N. General Assembly and applied for a visa to enter the U.S. The State Department said Washington received a visa request but that before going to U.N. headquarters, al-Bashir should present himself to the ICC.
Sudan condemned Washington's response, and Sudan's Foreign Ministry said the U.S. is "not qualified ... to offer sermons and advice" on international law and human rights. Sudan's statement also criticized U.S. support for Israel, and called on Washington to swiftly grant al-Bashir a visa.
AP Technology Writer Barbara Ortutay in New York contributed to this report.