Military forces arrested several members of Sudan's civilian leadership before dawn on Monday, Al Hadath TV reported, as a prominent pro-democracy group called on Sudanese to take to the streets to resist any military coup.
Family sources told Reuters that military forces had stormed the house of Sudan's Prime Minister Abdalla Hamdok's media adviser and arrested him.
There was no immediate comment from the military. Sudanese state TV broadcast as normal.
Reuters witnesses said internet services appeared to be down in the capital, Khartoum.
Citing unidentified sources, Al Hadath said Hamdok had been placed under house arrest, and that unidentified military forces arrested four cabinet ministers, one civilian member of the ruling Sovereign Council, and several state governors and heads of political parties.
Sudan has been on edge since a failed coup plot last month unleashed bitter recriminations between military and civilian groups meant to be sharing power following the 2019 ouster of former leader Omar al-Bashir.
Bashir was toppled and jailed after months of street protests. A political transition agreed after his ouster was meant to lead to elections by the end of 2023.
As tensions built this month, a coalition of rebel groups and political parties aligned themselves with the military. Supporters of the military have been staging a sit-in outside the presidential palace calling on the military to dissolve the civilian government.
Last week, several cabinet ministers took part in big protests in several parts of the Khartoum and other cities against the prospect of military rule.
The military head of the Sovereign Council has previously asserted his commitment to the transition.