The man suspected of bombing a McDonald's restaurant in a failed bid to extort money from the fast food chain has been detained by police.

Xu Yonggang, 28, was seized as he was travelling by bus from Hanzhong, in Northwest China's Shaanxi Province, to the provincial capital of Xi'an.

He is being quizzed over the June 15 bombing of McDonald's in Xi'an, which caused serious damage to the property.

Police said the bomb was a crudely made device that had been planted in the men's toilet of the Gulou branch of the fast food chain in the city.

Police allege that Xu decided on the bombing after falling heavily into debt from playing the lottery for two years.

Xu sent threatening letters to four restaurants and supermarkets in the city on June 14, saying he would target them with explosives if they did not give him money, police claim.

All the restaurants and supermarkets reported the demands to the police and did not pay any cash.