A Ukrainian lawyer and former politician has been gunned down in a 'professional hit' by a motorbike-riding assassin while dropping his daughter off at a prestigious American school in Madrid.

Andriy Portnov, who last year won a defamation case against a Ukrainian news site that called him 'pro-Russian', was shot five times moments after dropping off his child in the upmarket Pozuelo district of the Spanish capital.

Police received the call about the shooting at 9.15 a.m. (0715 GMT) local time, the Madrid police told Reuters, without identifying the victim.

The man was said to have been shot five times as he took his children to the school when he was shot. His body was still at the scene nearly two hours after the shooting and will be only be removed following authorisation from a judge.

Police have not yet made any official comment but well-placed sources are describing it as an 'ajuste de cuenta' - which translates into English as a 'settling of scores' or 'revenge killing.'