LAHORE, DEC 25: A series of bomb explosions in three Pakistani cities today injured 45 people, police said.The first bomb ripped through a crowded market in the eastern border-city of Lahore, injuring 36 people, while the second bomb exploded at a railway station in Faisalabad, also in eastern Punjab province, wounding three people, they said.The third explosion occurred in a passenger bus in Hyderabad in the southern Sindh province, injuring six people.No group has claimed responsibility for any of theexplosions.``We are on alert. We have called the reserve police force, beefed-up the security and are trying to arrest culprits,'' Malik Asif Hayyat, Inspector of Punjab Police, said.The explosion in Lahore caused a fire that destroyed several makeshift wooden stalls and shattered glass in nearby buildings in Lunda Bazaar, located near the congested Delhi Gate neighbourhood, he said.The bomb was apparently placed in a shopping bag left by an unidentified man near one of the roadside stalls. The explosion triggered a stampede as fire and smoke billowed from the stores.The bombing occurred as people were busy shopping for Pd-ul Fitr. The festival begins on Wednesday.In Faisalabad, the bomb exploded at a time when there were few people at the railway station.Pakistan has been rocked by dozens of explosions, this year. The relentless bloodletting has killed more than 100 people.