Sebastian Vettel was narrowly out-qualified by Kimi Raikkonen at Monza

Ferrari have revealed to Sky Sports they spent "a few tokens" on developing their engine ahead of the Italian GP.

It's understood that the Scuderia used three of their remaining tokens, leaving the team with four to be deployed in the remainder of 2015.

The long straights at Monza demand a strong engine and Ferrari's improvements were immediately noticeable with Kimi Raikkonen two tenths of a second behind pole-sitter Lewis Hamilton despite Mercedes spending seven tokens of their own on development this week.

The sister Ferrari of Sebastian Vettel also out-qualified the second Mercedes of Nico Rosberg, who was running the older Mercedes engine following unreliability problems in final practice, underlining the progress the Scuderia have made.

Team principal Maurizio Arrivabene had confirmed after Friday practice that tokens had been spent, but had declined to comment on what area.

"We've spent a couple of tokens here but we have a little improvement but we are far from this super engine that has been mentioned, a lot of time," he said.

"I can confirm that we have spent a couple of tokens but I don't confirm that we have a super engine here. We have a Ferrari engine, this is enough."

Sebastian Vettel starts third at Monza, behind Kimi Raikkonen who lines-up second

Sky Sports sources at Ferrari have revealed that the tokens were spent on ICE development.

However, the team have been keen to downplay their impact, instead pointing out that the stop-start nature of the long blasts punctuated by slow chicanes plays into their hands - as demonstrated by Vettel's charge from 18th to fifth in Canada and setup changes they had made overnight before Saturday's qualifying session at Monza.

Vettel was circumspect when discussing the updates, suggesting the team had spent their tokens simply to perform better in front of their home crowd, the Tifosi.