Uruguay-born Sebastian Quintana fired a dramatic late equaliser to earn Qatar a 1-1 draw against holders Japan in their Asian Cup opener on Monday.

Naohiro Takahara's close-range strike after 61 minutes had looked good enough for Japan until Quintana's deflected free kick flew into the top corner in the 88th minute.

"We were careless!" Japan coach Ivica Osim fumed after his side's failure to kill off the game. "This result could make it difficult for us. The players have got to learn to turn style into substance."

Eintracht Frankfurt striker Takahara clinically tucked in Yasuyuki Konno's flicked cross with a left-foot volley for his 20th goal in 48 internationals.

But Japan were undone after Yuki Abe's clumsy foul on Quintana, who blasted the subsequent free kick past Yoshikatsu Kawaguchi from 25 metres with the help of a deflection.

Japan, bidding for a third straight Asian Cup title, trail Vietnam in Group B after the co-hosts' 2-0 win over United Arab Emirates 2-0 at the weekend.

Even a red card shown in stoppage time to Hussain Yaser failed to dampen the joy of Qatar coach Dzemaludin Musovic, who was also ordered down the tunnel for protesting the decision.

"Of course Japan won't be happy with the result," said Musovic, who was assistant to Osim when he led Yugoslavia to the quarter-finals of the 1990 World Cup.

"But we deserved to take a point and I think we can be a danger to any team in the tournament now."

Japan playmaker Shunsuke Nakamura said Qatar's last-gasp equaliser had shocked the holders, who never really hit their stride in Hanoi's clinging humidity.

"We were in control and then it was just a sense of 'ugh!' when they scored," Nakamura told Reuters.

"We need to learn to finish the game off with a second goal."

The Celtic midfielder added: "Abe feels gutted right now after the foul but we'll bounce back."

Japan face UAE in their second game on Friday. Qatar play Vietnam a day earlier.

This year's tournament is being staged jointly by Vietnam, Indonesia, Malaysia and Thailand. The final is in Jakarta on July 29.

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