Several drivers for the alternative taxi service Uberpop have been sent warnings by the transport ministry, saying they face fines of up to €4,200 if they continue to transport people for money, Nos television said on Friday.

Uberpop, launched in Amsterdam last month, allows private car owners to operate as taxis through an online matching service. Nos did not say how many drivers have been threatened with a fine.

However, the transport ministry said earlier the Uberpop set-up breaks existing laws requiring taxi drivers to be licenced and that it would come down hard on drivers who joined the scheme.