N'DJAMENA - A number of people were hurt in Chad, some severely, in gunfire celebrating interim President Mahamat Idriss Deby's declared election victory on Thursday, the health ministry said, ordering hospitals to take urgent steps to help the worst cases.

Overnight, volleys of shots could be heard in the capital N'Djamena in the hours after the state election agency said Deby had won a hefty 61.3% of the vote on May 6, even as his main challenger rejected the result and called for protests.

In a statement on Friday, the health ministry did not say how many people had been injured, and did not mention any deaths, despite unconfirmed reports that some people were killed.

"The exact number of victims is unknown, but there is already talk of around 10 dead, including children," Amnesty International researcher Abdoulaye Diarra told Reuters.

Madjissem Neldjibaye, who lives in N'Djamena's 9th district, was lying on his bed when a falling bullet struck his arm.

"To get to the hospital, I had to leave the house at 1 a.m. because people were shooting in all directions. I couldn't get out," Neldjibaye told Reuters at his home, describing how he pulled the bullet out himself.

Once he got to the hospital, Neldjibaye said he saw many people with similar injuries, some far more severe than his own.

If he had arrived earlier, "they wouldn't even have had time to treat me, because they were swamped," he said, his arm patched with a small bandage.

The chaotic celebrations followed a fraught electoral period marked by the killing of opposition figure Yaya Dillo in February, the omission of prominent opposition politicians from the candidate list, and other issues that critics say undermined the credibility of the vote.

N'Djamena was calm on Friday with little sign of the leading challenger Succes Masra's supporters taking to the streets. There was a heavy police presence including convoys of vehicles filled with men in camouflage fatigues patrolling the nearly empty streets.

However, Masra's Transformateurs party, which has been keeping a parallel vote tally, said on Friday he had won, based on their count. "We have the evidence and Chadians all know it," the party said in an online post.

It was not immediately clear if Masra or his party planned to mount a formal legal challenge to the results.

The presidential election makes Chad the first of the coup-hit countries in West and Central Africa to stage a return to constitutional rule via the ballot box, although Masra and other opposition factions have cried foul over transparency concerns.

Abdou Abarry, Special Representative of the U.N. Secretary General in Central Africa, called on all parties to show restraint.

(Additional reporting by David Lewis Additional reporting and writing by Alessandra Prentice; Editing by Ros Russell and Frances Kerry)