BANGKOK — A police manhunt was underway in Thailand for an “unidentified foreign man” shown in a security video leaving a backpack at a popular Bangkok shrine just minutes before a bomb exploded there.

Two other people seen on the video near the man are also considered suspects in Monday’s deadly bombing, police said late Wednesday.

Authorities released a sketch of the man who left behind the backpack and offered a 1 million baht ($28,000) reward for information leading to his arrest. But apart from the rough portrait, they had few solid leads in Monday’s bombing at the Erawan Shrine that killed 20 people and wounded 120 others.