Italian Grand Prix 2015: Lewis Hamilton raises the bar at Monza to lay down the gauntlet to Mercedes rival Nico Rosberg

Hamilton topped first practice at Monza as Mercedes dominate in Italy

Hamilton negotiates the first chicane (Getty Images)

Lewis Hamilton laid down the title gauntlet to Nico Rosberg in opening practice for the Italian Grand Prix.

Hamilton was almost half-a-second clear of his Mercedes team-mate Nico Rosberg, who became a father for the first time this week, after posting a best lap of one minute 24.670secs.

The Mercedes pair were in a league of their own in Monza, with Ferrari's Sebastian Vettel a mighty 1.6sec slower than Hamilton.

Nico Hulkenberg, who signed a new two-year deal with Force India earlier this week, was the only other driver within two seconds of Hamilton.

Pirelli, Formula One's sole tyre supplier, are under the spotlight in Italy after two high-profile blow-outs at the Belgian Grand Prix.

Vettel claimed he could have been killed following his penultimate lap puncture while Rosberg was fortunate to emerge unscathed from a 190mph blow-out during practice.

Hamilton sports a new blond hairstyle ahead of practice (Getty Images)

Pirelli urged the teams to run higher tyre pressures in practice - a concept which Hamilton claimed could have disastrous repercussions.

However, there were no signs of the tyre trouble which overshadowed the British driver's sixth victory of the season in Spa.

Instead it was Hamilton, sporting a new blond hairstyle in Italy, who turned in an emphatic display to leave Rosberg trailing on the quickest circuit of the year.

Hamilton, who is 28 points clear of Rosberg in the championship, was 0.463sec faster than his Mercedes team-mate.

The session was red flagged after 30 minutes when Carlos Sainz lost control of his Toro Rosso under braking at the Parabolica and beached his car in the gravel.

"I don't know why I lost the car," the 21-year-old Spaniard reported over the team radio.

But when his Toro Rosso was removed and the session re-started, it was the turn of his team-mate, Max Verstappen, to be caught out at the same corner.

Lewis Hamilton topped first practice in Monza (Getty Images)

The 17-year-old Dutchman managed to catch the back of his unruly Toro Rosso and kept it on the asphalt.

McLaren, enduring a woeful season, were again at the back of the field.

Fernando Alonso, who will serve a 10-place grid penalty after yet another engine change, was 17th, 3.3sec down on Hamilton's best lap. Button, who too will have a grid penalty on Sunday, was 18th, four tenths adrift of his team-mate.

Elsewhere, Sergio Perez, closing in on a new deal with Force India, was fifth fastest with Ferrari's Kimi Raikkonen, Red Bull's Daniel Ricciardo, the Williams duo of Felipe Massa and Valtteri Bottas and Pastor Maldonado in his Lotus completing the top 10.

Each of the 20 drivers sported stickers on their crash helmet in tribute to Justin Wilson, the 37-year-old Briton who was killed last month in an IndyCar race in Pennsylvania.

Final Times after First Practice:

1 Lewis Hamilton (Gbr) Mercedes GP 1min 24.670secs,

2 Nico Rosberg (Ger) Mercedes GP 1:25.133,

3 Sebastian Vettel (Ger) Ferrari 1:26.258,

4 Nico Hulkenberg (Ger) Force India 1:26.612,

5 Sergio Perez (Mex) Force India 1:26.730,

6 Kimi Raikkonen (Fin) Ferrari 1:26.783,

7 Daniel Ricciardo (Aus) Red Bull 1:26.922,

8 Felipe Massa (Bra) Williams 1:26.936,

9 Valtteri Bottas (Fin) Williams 1:27.075,

10 Pastor Maldonado (Ven) Lotus F1 Team 1:27.118,

11 Felipe Nasr (Bra) Sauber-Ferrari 1:27.232,

12 Daniil Kvyat (Rus) Red Bull 1:27.275,

13 Marcus Ericsson (Swe) Sauber-Ferrari 1:27.454,

14 Max Verstappen (Ned) Scuderia Toro Rosso 1:27.591,

15 Jolyon Palmer (Gbr) Lotus F1 Team 1:27.669,

16 Carlos Sainz (Spa) Scuderia Toro Rosso 1:27.907,

17 Fernando Alonso (Spa) McLaren 1:28.023,

18 Jenson Button (Gbr) McLaren 1:28.423,

19 Will Stevens (Gbr) Manor Marussia F1 1:29.853,

20 Roberto Merhi (Spa) Manor Marussia F1 1:29.911

PA