Yet to finish off the podium after seven races, the 22-year-old Hamilton extended his lead at the top of the world championship to ten points from Alonso who was second, 1.5 seconds behind Hamilton who took full advantage from pole position.

Brazilian Felipe Massa was third for Ferrari ahead of Finnish teammate Kimi Raikkonen in fourth, while another Finn, Heikki Kovalainen, was fifth for Renault and Italian Jarno Trulli finished sixth in a Toyota.

"What a dream," an emotional Hamilton told reporters.

"I never thought in a million years I would be here today with these drivers and win two races in North America.

"To come to Canada for the first time and now Indianapolis for the first time and have the best two races of my life, it's an amazing feeling.

"Coming into the season you have to be realistic, I never expected anything but hoped to do well," he added.

"I hoped maybe I could get a podium at some point but I have been on the podium the last seven races. It's insane."

Start to finish for Hamilton

Victory also increased Hamilton's chances of becoming the first rookie world champion since Italy's Nino Farina in 1950.

The Brit worked hard to stay in front of his teammate through the first corner of the race, but the major drama was further back where under-pressure Toyota driver Ralf Schumacher, Honda's Rubens Barrichello and Red Bull's David Coulthard all had their races ended prematurely by a crash.

The incident could be particularly damaging for Schumacher whose race seat is rumoured to be under threat after a poor season so far.

Hamilton opened up a 2.2 second lead from Alonso after ten laps with Massa 4.5 seconds behind, and continued to creep clear, regularly setting fastest laps before the first round of pit-stops after 20 laps.

Alonso attacks

When the cars emerged from their stops in the same order, Alonso began to attack Hamilton cutting the gap to under a second after 32 laps, however Massa was then over 13 seconds behind the leaders.

Ferrari have dominated recent races at Indianapolis, winning six of the previous seven, but they never threatened the McLarens on this occasion.

Alonso pulled alongside Hamilton at the start of lap 38 but Hamilton dramatically, desperately, and skilfully, resisted his more illustrious teammate, and after pitting for the last time on the 51st lap there was no change in the running order.

It was McLaren's third win in a row after Hamilton in Canada and Alonso in Monaco last month, and also their third 1-2 finish in a row.