Australian Daniel Ricciardo charged to a thrilling Hungarian Grand Prix victory on Sunday, his second Formula One win for Red Bull, as a drenched track caused chaos among world championship leaders.

Rivalry between Lewis Hamilton and his Mercedes teammate and championship leader Nico Rosberg reached a new peak as Hamilton rebuffed team orders to let Rosberg by into third place.

Mercedes said it would hold a team inquiry. But Hamilton's success trimmed Rosberg's lead in the title race from 14 points to 11. The German now leads with 202, Hamilton has 191 and Ricciardo is third with 131.

Ricciardo, 25, held off Ferrari's Fernando Alonso to take first place in a race which saw several high-speed crashes after a heavy downpour just before the start changed the course of the race.

Ricciardo led twice before he fought back to recapture the lead with three laps remaining, following a series of daring passes.

Ricciardo's win was executed with great elan and confirmed him as a driver with the potential to be a future champion.

Ricciardo won the Canadian Grand Prix in June and is the only non-Mercedes driver to have won a race this year.

"This feels just as good as the first one," said Ricciardo. "It was a lot of fun in the last few laps, with the passing. I had to go for it."

Hamilton and Rosberg had a fierce battle on the track and via the Mercedes team radio as they tried to make the most of contrasting strategies in the changeable conditions.

Hamilton started from the pit lane along with rookies Daniil Kvyat of Toro Rosso, who had stalled on the formation grid, and Dane Kevin Magnussen, who crashed his McLaren in qualifying.

Hamilton was running with cold brakes in a car rebuilt overnight following the blaze, caused by a fuel leak.

Pushing to make up places, he spun on his opening lap and brushed the barriers at Turn Two. "My front left hit the wall.

The brakes just gave up," said Hamilton.

Another crash, when Swedish rookie Marcus Ericsson lost control of his Caterham, on lap eight brought out the Safety Car.

Jenson Button in a McLaren took the lead for a while but as the conditions changed he had to pit. This put Ricciardo back on top again.

Hamilton, sensibly, had pitted and was soon back up to ninth, within two cars of Rosberg, as the field, shuffled heavily by the rain and the Safety Car, began to settle again.

Both Force Indias were soon among the list of retirements. German Nico Hulkenberg crashed out at Turn One, after clipping team-mate Mexican Sergio Perez, and soon after Perez lost control at the final corner and spun heavily into the walls.

The Safety Car came out for a second time and Ricciardo pitted again from the lead, gifting Alonso the rarity of running at the front for Ferrari as the beleaguered Italian team struggled to end their poor form.

On lap 33, Sebastian Vettel's Red Bull car spun at the final corner and down the straight, saving himself from disaster by kissing the wall. Rosberg pitted, endured a problematic stop, and rejoined 13th.

Offered his chance, Hamilton seized it. On lap 34, he delivered a sublime pass round Jean-Eric Vergne in a Torro Rosso to take second and begin the chase after Alonso.

Alonso finally pitted again after lap 38 and Hamilton, from a pit lane start, took the lead. It lasted one lap before he pitted again, for medium tyres, rejoining fifth behind Alonso with Ricciardo leading.

On lap 47, Hamilton's race engineer Pete Bonnington warned him "Nico is behind and on the option tyres so don't hold him up."

Further warnings followed but Hamilton declined to heed them.

"I'll let him through if he gets closer," he said. "I'm not slowing down for Nico..."

Rosberg pitted again with 13 laps remaining. He rejoined seventh and battled his way to fourth and finished half a second behind Hamilton.

Rosberg said after he had been told by the team that Hamilton would let him by. "I don't know what happened," he said, saying it would have to be discussed "internally".

Mercedes cheif Toto Wolff said there would be "no knee-jerk reaction" to Hamilton's actions and there would be an internal inquiry.

Brazilian Felipe Massa of Williams finished fifth ahead of Finn Kimi Raikkonen, in the second Ferrari, defending four time champion German Sebastian Vettel in the second Red Bull and Finn Valtteri Bottas of Williams.

Nico Rosberg had mixed feelings again on Saturday when he claimed his sixth pole of the season for Sunday's Hungarian Grand Prix after Mercedes team-mate Lewis Hamilton's car burst into flames on his opening lap.

The world championship leader took full advantage of Hamilton's bad luck and admitted he felt less than ecstatic at his success and would have preferred to have competed against his main title rival.

The 29-year-old German, who leads Hamilton by 14 points in their duel for the drivers' title, cashed in after the luckless Briton's car burst into flames in the opening minutes of a dramatic qualifying session.

"It's a pity for the team and for me," said Rosberg. "Again it's reliability and, also, I would prefer to be battling with Lewis and have the maximum adrenaline rush and not be like this... It's not the same.

"I am not so happy and not ecstatic about it."

Rosberg clocked a best lap of one minute and 22.715 seconds to claim his sixth pole of the year and the 10th of his career in an hour that saw intense heat, at the start, followed by dark clouds and rain in the final minutes.

He added: "Q3 was a big challenge. The track was changing all the time at the beginning I was the first one into the first corner. It was very difficult to judge. It was very wet.

"So, I took it easy and I managed to avoid crashing. It was massively difficult and unpredictable. And then it was drying and it was much easier and I managed to nail it with my last lap."

Reading the weather conditions in advance, Rosberg was first car out in Q3 and ran wide at Turn One shortly before Danish rookie Kevin Magnussen flew off and into the barriers at the same place.

That caused red flags and the session was halted for five minutes, resuming in damp, but drying conditions as the hot sunshine resumed - a scenario that saw a series of drivers in serious contention for pole.

Vettel clocked a best lap of 1:23.201 that put him clear at the top in the final seconds, but Rosberg responded to outpace him by 0.486 seconds to secure the prime starting position.

Finn Valtteri Bottas was third for Williams ahead of Australian Daniel Ricciardo in the second Red Bull, two-time champion Spaniard Fernando Alonso of Ferrari and Brazilian Felipe Massa, sixth for Williams.

Vettel said: "I think the nature of the track here suits us better, there are less straights and historically we have always had a competitive car around here.

"It is nice to be a little bit closer to Nico, but his lap still gave him a bigger gap at the end than we had hoped for..."

Bottas said: "I think it is a little bit of a surprise for me to be here, but the team has worked hard and the upgrades have worked well. It is a good day for us."

Briton Jenson Button, twice a winner in Hungary, in wet conditions, was seventh for McLaren ahead of Frenchman Jean-Eric Vergne of Toro Rosso, German Nico Hulkenberg of Force India and Magnussen.

"We'll have to replace the engine and gearbox, but with that penalty it's a good thing (for a gearbox change)," said Hamilton. "I can't go any further back.

"There's a lot going through my mind, but I just have to try to turn it into positives until tomorrow. I think it's getting to the point beyond bad luck - it's something else. We just need to do better."

Earlier on a day of less-stifling heat than Friday, with a track temperature of a relatively modest 46 degrees Celsius, Hamilton was the second man eliminated in Q1, his car blazing from a first lap fuel leak just after Venezuelan Pastor Maldonado had idled to a halt in his Lotus.