[MADRID] The Spanish government said on Wednesday it was hunting for the authors of malicious jokes on Twitter about the victims of the air crash in the French Alps.

"If they were all Germans and Catalans, what is the tragedy?" wrote one user, flagging the Tweet with the hashtag #Germanwings.

"It is not the first time the social networks are used for hate speech," which is punishable under Spain's penal code, said junior security minister Francisco Martinez.

"The interior ministry has ordered an investigation to establish possible criminal responsibility for messages posted on social networks," he told a news conference.

"As well as expressing tremendous cruelty, they may constitute crimes which will have to be investigated and referred to the justice system."

Many of the messages appeared to target Catalans, inhabitants of the culturally distinct Catalonia region and regular targets for teasing in the rest of Spain.

The plane took off from Barcelona, capital of Catalonia, before it crashed in southeastern France on Tuesday with the deaths of all 150 people on board.

The Spanish government said at least 49 Spaniards were among the victims but Germanwings, the airline operating the flight, said there had been 35 Spanish victims.

Spain's interior ministry launched a crackdown on online hate speech in May 2014 after the killing of a ruling party politician sparked many insults online against conservative politicians.

AFP