Embodiments of the disclosure provide a method, an apparatus, a network node, and a computer program product for transmitting D2D synchronization signals. According to the method, D2D synchronization signals are received from a first network node. A hop number of the D2D synchronization signals is determined based on radio resources of the D2D synchronization signals. Whether to transmit the D2D synchronization signals to a second network node is determined based on the hop number.