SHANGHAI (Reuters) - The man responsible for a weekend blast at Shanghai's Pudong International Airport that injured five people, including himself, was an indebted gambler who warned on Chinese social media that he intended to kill himself, police said on Monday.

Zhou Xingbai, a 29-year-old migrant worker from the southwestern province of Guizhou, posted his message in the early hours of Sunday, the police said on their official Weibo microblog.

On the messaging app WeChat, Zhou said that he owed a lot of money, and was "preparing to commit an extremely crazy act which will almost certainly lead to my death," the police said.

Zhou threw self-made explosive packed in a beer bottle at a ticketing counter in the airport's Terminal Two, and slashed his own neck after the explosion, authorities said.

Reuters was unable to independently contact Zhou.

Zhou, who was employed by an electronics firm in the nearby city of Kunshan, was heavily in debt from Internet gambling and dependent on loans from friends, after having lost his life savings, the police said.

He used public transport on Sunday to travel to the airport from Kunshan, where police later found fireworks and explosive materials in his rented flat, they said, adding that the case was still being investigated.

Explosives are relatively easy to obtain in China, home to the world's largest mining and fireworks industries.

(Reporting by Brenda Goh; Editing by Clarence Fernandez)