The present invention provides oligonucleotides and methods for efficient detection of target nucleic acids using rolling circle replication. In one aspect, the oligonucleotides of the invention are characteristic in that they can be circularised without an external ligation template. In another aspect, the oligonucleotides of the invention are characteristic in that they can generate a free 3′end of the target nucleic acid necessary for rolling circle replication. The oligonucleotides and detection methods of the invention are useful e.g. as research tool and for diagnosis.