The Muslim Brotherhood's Mohamed Morsy said on Monday after his group declared him winner in a presidential race that he would be a president for all Egyptians and said he would not "seek revenge or settle scores."

Morsy was speaking at a news conference after the Brotherhood declared he had won 52.5 percent of the vote compared to the 47.5 percent secured by his rival, ex-military man Ahmed Shafik, with almost all votes counted. Shafik's campaign challenged the result.

"Thanks be to God who has guided Egypt's people to the path of freedom and democracy, uniting the Egyptians to a better future," Morsy said.

He promised that as president he would not "seek revenge or settle scores."

He pledges to serve both those who voted for him and those who did not and also vowed to seek justice for those killed in the uprising that toppled Hosni Mubarak last year. More than 850 people died in the uprising, and dozens more have in violence since then.

"To all the martyrs and to their families ... I pledge to return their rights through law and in a law-abiding nation," Morsi said, speaking at the Cairo headquarters of the Brotherhood's Freedom and Justice Party.

Brotherhood officials said the results were initial because there were still appeals to be filed.

"We are reaching out to Shafik's campaign to end the elections race and competition and to part amicably as friends," Morsy campaign official Yasser Ali said.

But shortly before the final result the generals who have run the country since the overthrow of Mubarak issued new rules in a constitutional declaration outlining the president's powers that made clear real power remains with the army.

"We will sit with the military council to discuss the constitutional decree amendments which we refuse fully and will go to Tahrir Square next Tuesday to protest against these amendments," Ali said.

He also said Morsy would only accept to swear an oath before the parliament that was dissolved by a court order last week. (Reporting by Marwa Awad and Samia Nakhoul; Writing by Edmund Blair)