Egypt's military rulers vowed Thursday that this month's presidential election will be fair and moved to assure the public it will hand over power on schedule, a day after a deadly attack on an anti-military protest.

The Supreme Council of the Armed Forces, which took power when president Hosni Mubarak was ousted by a popular uprising last year, also warned against any threat to the defence ministry, as protesters called for mass rallies on Friday.

"We are committed to fair elections 100 percent. We don't have any candidates. All the candidates are respectable Egyptians," said Major General Mohammed al-Assar of the Supreme Council of the Armed Forces.

Assar said that the electoral commission "sent a letter to the foreign ministry requesting that it invites 45 foreign observers to monitor the presidential election."

"The commission also sent messages to all the embassies inviting them to send a delegate to monitor the election and issued permits to three foreign organisations as well," he added.

Assar was speaking at a news conference as calm returned to Cairo's streets following clashes that killed 20 people outside the defence ministry on Wednesday, according to medics.

"We want to stress the commitment of the armed forces... of not using violence against the people. The armed forces belong to the people," said Assar, who put Wednesday's toll at nine dead and said more than 160 were injured.

The general, an aide to the defence minister, said the security forces had intervened "positively" to stop the bloodshed and to ensure stability, more than a year after a popular uprising toppled Mubarak.

"Egypt is in danger... Everyone must realise this danger," said Assar.

"I propose an initiative to all political parties and religious leaders to go to Abbassiya and try to persuade the youths to leave Abbassiya," he said referring to the Cairo district in which Wednesday's clashes occurred.

"Go to Tahrir Square... to stay away from the defence ministry because we dont want to use any violence against our youths," he added.

In stronger terms, the military warned protesters to stay away from the defence ministry, following calls for a mass protest on Friday to denounce Wednesday's deadly clashes.

The pro-democracy April 6 movement -- one of the groups that helped launch last year's revolt-- as well as the powerful Muslim Brotherhood both said they would take part in Friday's rallies in statements on their websites.

"The responsibility, the duty, the law and the right to self-defence, as well as the honour of the military obligates members of the armed forces to defend the defence ministry and its military installations because they are a symbol of military honour and the prestige of the nation," General Mokhtar al-Mulla, a member of the ruling military council, said on Thursday.

"If anyone approaches its (installations), they should hold themselves responsible," he told reporters.

Cairo's Tahrir Square was the epicentre of the massive protest movement that eventually forced Mubarak to hand over power to the military, led by Field Marshal Hussein Tantawi.

Assar said the military would transfer power by the end of June.

The presidential election is scheduled for May 23 and 24 and a run off for June 16 and 17 if there is no outright winner in the first round.

"We have said and repeated since November 2011 that the Supreme Council is committed to handing over power before June 30, 2012. And today we say it again clearly and frankly: the SCAF is committed to handing over power by June 30, 2012 and even before," said Assar.

"We have no wish to stay in power. We do not want power. The supreme council is not an alternative to legitimacy," he added.

Critics of the military rulers cried foul after the electoral commission disqualified 10 of the 23 candidates vying for the presidential race, saying they did not meet the proper criteria.

Assar stressed that the SCAF, under whose rule parliamentary elections took place late last year and early this year, were not tampering with the polls.

He also urged the armed forces to remain steadfast urging them "not to listen" to abuse expressed by their detractors.

"The people appreciate your historic positions," Assar said.

"After July 1, it will be said that the SCAF played a historic role" in the transition of Egypt from Mubarak's autocratic regime to democracy, he added.

[Thousands of anti-military demonstrators protest near the ministry of defence in Cairo on May 2. AFP Photo/Gianluigi Guercia]