UNITED NATIONS, United States (AFP) - Saudi Arabia's angry rejection of a Security Council seat one day after winning it stunned members of the body on Friday.

But diplomats said there had been no official notice from Riyadh of its refusal to take up the seat on January 1. It was possible the conservative kingdom could change its mind, they added.

"This is totally unexpected. We all had to look into the council history for a precedent and there is not one," said a Security Council diplomat, speaking on condition of anonymity.

"Campaigning and securing a seat normally takes years of preparation which makes the announcement even more surprising."

Saudi Arabia was one of five nations elected by the UN General Assembly to start a two-year term on the 15-member Security Council. The others included Chad, Chile, Lithuania and Nigeria. All had stood unopposed.

"There was nothing controversial about the election. But the government has made it clear in recent weeks that it is concerned about Syria and the Palestine issue," said a second UN diplomat.

"They will have to write to set out their official position and then the UN will have to decide the next step," the envoy added.

"There could be a new election, but it is possible that Saudi Arabia can be persuaded to change its stance."

The United Nations secretariat and UN General Assembly president had no immediate comment.

Saudi Arabia won a seat for the first time in Thursday's election.

"Work mechanisms and double-standards on the Security Council prevent it from carrying out its duties and assuming its responsibilities in keeping world peace," the Saudi foreign ministry said in a statement explaining its move.

"Therefore Saudi Arabia... has no other option but to turn down Security Council membership until it is reformed and given the means to accomplish its duties and assume its responsiblities in preserving the world's peace and security," it added.