Sudanese army troops and allied militiamen were rapidly advancing in the capital on Wednesday, engaging the rival paramilitary Rapid Support Forces in street combat in residential areas once home to hundreds of thousands of citizens before the war broke out 21 months ago.

The Sudanese army has broken a siege by the paramilitary Rapid Support Forces of its command centre in central Khartoum, the army said on Friday, in what would be a major victory in the capital after nearly two years of war.

The Sudanese army said Wednesday it had launched a multi-pronged attack reaching areas near the Khartoum oil refinery, 70 kilometres (43 miles) north of the capital. It is the first time the army has reported a presence near the strategic facility since the conflict began in April.