Ali Adnan swept home a brilliant, last-minute free-kick as former champions Iraq twice hit back to beat Vietnam 3-2 in the Asian Cup on Tuesday.

It was a heart-breaking way for Vietnam to lose in Abu Dhabi, but no more than Iraq deserved for going for the jugular after Humam Tareq had hauled them level on the hour mark.

"The first half was horrible," said Iraq coach Srecko Katanec.

"We showed nothing that we did in training -- no power, no personality at all. Maybe it was first-game emotions, the players felt the pressure a little bit."

"I knew it would be a tough game," added the Slovenian. "But the most important thing was the three points."

Vietnam's Golden Dragons took a shock lead after 24 minutes in the Group D clash in Abu Dhabi, defender Ali Faez panicking under pressure from Nguyen Cong Phuong and clumsily backheeling the ball past goalkeeper Jalal Hassan Hachim.

Iraq, who defied the odds to win an emotional Asian Cup title in 2007, levelled 10 minutes later through striker Mohanad Ali, who profited from a defensive error to rifle home from the edge of the box.

Cong Phuong restored Vietnam's lead three minutes before the break, stabbing in from close range after Nguyen Trong Huang's shot had been parried by Hachim.

But Tareq lashed home a second equaliser following more horrific defending from the Vietnamese, who by that point looked to be running out of steam.

A lazy foul on the edge of the penalty area subsequently presented Adnan with the chance to take all three points and he did not disappoint, curling a left-foot shot into the top corner, prompting several Vietnamese players to slump to the turf in despair.

Iraq join Iran on three points after their bitter rivals thrashed Yemen 5-0 on Monday.

Iraq's circumstances have scarcely improved since thir fairytale success 12 years ago, with security concerns impacting their preparations for tournaments.

But the Lions of Mesopotamia will hope to at least match their run to the Asian Cup semi-finals in Australia four years ago, despite losing several of their top players to retirement.

"If we want to go deep into the tournament we will have to improve," shrugged Katanec.

"But I have a clearer picture now of our overall condition and we will grow into the tournament."

Vietnam coach Park Hang-seo, who steered his side to the southeast Asian title last December, insisted he had no regrets.

"I'm proud of my players," said the South Korean. "At the end they were exhausted and lost a bit of concentration but we were a little unlucky too."

"We were targeting a point from this game because we play Iran next and obviously they're title favourites," he added.

"It will be very tough from here but we will go again."