A Chinese national was stabbed to death by a mugger near the construction site of the 8th Bangladesh-China Friendship Bridge over Kocha river of Sadar upazila in Pirojpur district on Wednesday evening.   The deceased was identified as Lau Phan, 58, the chief technician of the project, said said Masud Mahmud Sumon, executive engineer of Roads and Highways Department in Pirojpur.      A mugger stabbed Lau at Kumirmara village around 6pm when he was going to the project site by a bicycle to pay wages of workers, said Mostafizur Rahman, interpreter for Chinese citizen of the bridge.   Being rescued, he was rushed to Pirojpur District Hospital where he died around 7:30pm, he said   Dr Nizam Uddin, resident medical officer of the hospital, said that the Chinese citizen died due to excessive bleeding.   Nurul Islam, officer-in-charge of Sadar Police Station, said on information they went to the spot.   Molla Azad Hossain, acting superintendent of police in Pirojpur, said that police is conducting a drive to arrest the mugger.