CAIRO Sudan's two-month long war is extending across the country with the army and Rapid Support Forces (RSF) clashing in several areas on Friday.

Air strikes and anti-aircraft missile fire hit overnight in the Omdurman and Khartoum, two of the three cities that make up Sudan's wider capital. But the war has in recent days heated up in cities to the west of the capital, in the fragile Darfur and Kordofan regions.

In Al Fashir, capital of North Darfur state, a fragile truce fell apart as the two forces clashed in residential areas.

And in El Obeid, capital of North Kordofan and a transport hub between Khartoum and Darfur, where the RSF maintains significant presence, the paramilitary force clashed with the heavily armed Central Reserve Police.

The worst fighting has been in West Darfur, where militias backed by the RSF razed areas of the city and forced a mass exodus, residents and human rights monitors said. The West Darfur city of El Geneina has been worst hit by repeated militia attacks.

The United States said on Thursday it had suspended talks which had so far presented the only forum for discussions between the two sides, though it only resulted in short, often-violated humanitarian ceasefire agreements.

In recent days, fighting had also picked up between the army and RSF in Nyala, capital of South Darfur and one of Sudan's largest cities. Clashes continued on Friday in the south of Nyala, and a resident said civilians were killed but could provide no further details.

A new front in the fighting is also threatening to open in South Kordofan, where the rebel SPLM-N controls some areas. The army earlier this week accused the force of violating a long-held ceasefire agreement.

The fighting has caused more than 2.5 million to be displaced, hundreds of thousands of whom have fled across the border, including to Chad and Egypt.

It has created a humanitarian crisis with NGOs struggling to provide much needed medical and food aid.

On Saturday, medical aid agency MSF said its operations have been hindered by both parties, including rejected travel permits.

"MSF supplies have been confiscated, while armed groups have looted our facilities and beaten and violently threatened staff," it said in a statement.

(Reporting by Khalid Abdelaziz in Dubai and Nafisa Eltahir in Cairo; editing by Grant McCool)