Police said Sunday they have arrested three men on suspicion of triggering a string of explosions involving what appeared to be butane gas that struck two major Seoul transportation hubs.

Police took custody of the three separately on Saturday. The men are suspected of placing privately made explosives inside lockers set up at Seoul Station in the central part of the capital and Seoul Express Bus Terminal in the southern part of the city on Thursday, police said.

The explosions, which caused no injuries or deaths, occurred about half an hour apart -- the first at Seoul Station and then at the bus terminal. Police have suspected the explosives were homemade as they found traces of butane tanks connected to electrical wires in both locations.

The group comprises a 43-year-old man, who appeared to have acted as the leader; a 36-year-old man who allegedly purchased materials for making the homemade explosives; and another man, 51, who is accused of planting the explosives at the train and bus stations.

CCTV footage showed one suspect, which led the police to arrest the group of three.

The police, who had launched a probe into whether the explosions were planned acts of terrorism, are investigating the men to discover a motive for the crime and other details.

(Yonhap News)