The victory means Ulsan are second in Group E with six points, two behind leaders Nagoya Grampus while Beijing are third with four points.

The hosts made a good start to the game as they attacked from the outset. Joel Griffiths fell in the area after failing to connect with the ball but the referee waved away the penalty calls.

Beijing continued to press but were struggling to create any chances of note in the final third as Yang Hao's long-range effort brought a rare save from Kim Young-kwang.

Ulsan finally awoke as the game headed towards half-time as a Hyun Young-min free-kick was cleared by the defence and Slavcho lobbed the ball into the net but the referee ruled the goal out due to an earlier infringement.

Beijing had chances soon after the restart as Du Wenhui and Matic Darko both sent shots wide of the goal as they looked to take a swift lead.

But it was the visitors who made the breakthrough in the 70th minute when Oh rose highest inside the area and headed home Kim's free-kick.

The hosts pressed for an equaliser as Griffiths had another penalty appeal turned down when he tumbled inside the box while the Chinese found themselves frustrated by the Ulsan defence, who held firm to ensure the three points went the way of the Koreans.