Nigeria's Acting President Goodluck Jonathan dissolved the cabinet today in a further step to assert his authority a month after assuming executive powers, Reuters quoted government and presidency sources as saying. Jonathan took over as acting leader in early February during the three-month absence of ailing President Umaru Yar'Adua for medical treatment. Yar'Adua has since returned to Nigeria but remains too sick to rule. Yar'Adua's secretive return in the middle of the night raised fears that his inner circle of aides, led by his wife Turai, would fight to maintain their influence over Africa's most populous nation and seek to undermine Jonathan. But the acting president has moved quickly to assert his authority, demoting the former justice minister -- a close Yar'Adua ally -- and appointing respected ex-military general Theophilus Danjuma as one of his top advisers. He also sacked the country's national security adviser, a key member of Yar'Adua's inner circle.