A person draped in the Sudanese national flag stands in front of a burning pile of tyres during a protest in Khartoum. Reuters

Armed forces detained Sudan's prime minister over his refusal to support their "coup" on Monday, the information ministry said, after weeks of tensions between military and civilian figures who shared power since the ouster of autocrat Omar al-Bashir.

The joint military forces, the ministry said in a statement on Facebook, also detained civilian members of Sudan’s ruling council and ministers in Hamdok’s transitional government.

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Internet services were cut across the country and the main roads and bridges connecting with the capital Khartoum shuttered, it added.

Dozens of demonstrators set car tyres on fire as they gathered on the streets of the capital to protest against the detentions, an AFP correspondent said.

"Civilian members of the transitional sovereign council and a number of ministers from the transitional government have been detained by joint military forces," the information ministry said.

"They have been led to an unidentified location," it said.

Sudanese Prime Minister Abdalla Hamdok attends a meeting with the World Bank president, in Khartoum. AFP

It added later that "after refusing to support the coup, an army force detained Prime Minister Abdalla Hamdok and took him to an unidentified location".

US Special Envoy for the Horn of Africa Jeffrey Feltman said "the US is deeply alarmed at reports of a military takeover of the transitional government".

"This would contravene the Constitutional Declaration (which outlines the transition) and the democratic aspirations of the Sudanese people," Feltman said in a statement on Twitter.

"Any changes to the transitional government by force puts at risk US assistance."

The Khartoum airport was shut and international flights were suspended on Monday, the Dubai-based Al Arabiya TV channel reported, amid reports of a military coup. There was no announcement from the Sudanese government on the status of the airport.

Traffic moves on a street in Sudan's capital Khartoum. File/AP

A media witness reported that Sudanese military and paramilitary forces deployed across the capital Khartoum, restricting civilians' movements, as protesters carrying the national flag burnt tires in different areas of the city.

Khartoum airport was shut and international flights were suspended, according to Al Arabiya TV channel.

Citing unidentified sources, Al Hadath said Prime Minister Abdalla 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 party leaders.