Nigeria's vice-president has the right to perform all duties on behalf of sick President Umaru Yar'Adua without any formal transfer, a judge has ruled. It is the first of four cases aiming to clarify who rules Nigeria during Mr Yar'Adua's absence. He has been in a Saudi Arabia hospital since November. Ministers and the lawyer who brought the case said they were satisfied. But some critics want to see Vice-President Goodluck Jonathan become official head of state. Correspondents say the issue is so sensitive because of the ruling party's system of alternating power between north and south. While Mr Yar'Adua is a northerner, Mr Jonathan hails from the south. Northern powerbrokers may be reluctant to see a southerner take over officially before the next scheduled presidential election in 2011. 'No power vacuum' Justice Daniel Abutu said Mr Jonathan would only be legally regarded as "acting president" if he had received written instructions to do so. Christopher Onwuekwe, the lawyer who brought the suit against the government, said he felt the judge had upheld his case. He said he went to court only to confirm that the vice-president had the power to carry out the functions of the president. Justice Minister Michael Aondoakka welcomed the ruling, saying it showed there was no power vacuum and would allow ministers to get on with the business of governing. He said there was now no justification for the other three cases - due before court on Thursday - to go ahead. In one of the cases, rights lawyer and activist Femi Falana wants all decisions taken by the cabinet during the president's absence to be annulled. In another, the Nigerian Bar Association is demanding that he hand over power formally to Mr Jonathan. And a rights group wants Mr Yar'Adua declared "missing". In his first public remarks since falling ill, Mr Yar'Adua told the BBC on Tuesday he was in constant contact with his deputy. He said he was recovering and hoped to be able to return to Nigeria to resume his duties. Doctors say the president is suffering from acute pericarditis - inflammation of the lining of the heart. He also has a long-standing kidney complaint. Source: BBC