Landline internet connections were down across Sudan on Monday, a week after mobile online services were cut following a deadly crackdown on protesters.
Internet lines from the country's main provider Sudatel stopped working in the capital Khartoum in the early afternoon, an AFP correspondent said, adding the outage had affected embassies, luxury hotels and offices.
Cyber security monitor Netblocks said "an almost total blackout" started around noon local time.
"It's the first time Sudantel has cut off everything in the country," a spokesman for the group said.
"It was not switching off data centres, more like a digital cutting of all lines," he said, adding the monitor first noticed "signs of disconnection" at the weekend.
The cuts come as a nationwide civil disobedience campaign entered its second day against the country's ruling generals who took power after the ouster of longtime leader Omar al-Bashir in April.
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Protest organisers said the campaign would run until the generals handed power to a civilian government.
The campaign kicked off nearly a week after an assault on demonstrators at a sit-in outside the army headquarters in Khartoum left dozens dead and crushed hopes for a swift democratic transition.
Netblocks said current outages were different than previous internet shutdowns under Bashir, which were done "with a high degree of synchronisation".
"What we see now is that networks are going down then partially coming back," the spokesman said.