A motorcycle-borne suicide bomber on Thursday struck a bus carrying employees of a top Pakistani nuclear facility in Rawalpindi, killing one person and injuring 35 others, officials said.

Regional Police Officer Nasir Khan Durrani initially told reporters that six persons were killed in the attack, but later lowered the toll to one after confirming details of casualties with hospitals in Rawalpindi. “I was at the spot and was told the toll was five to six, but later we checked with hospitals and they confirmed that one person had died,” Durrani said.

An official of the state-run rescue service said 35 injured people were taken to hospitals.

The bomber, aged about 20 years, rammed his motorcycle into the fuel tank of the bus at a traffic light at a busy commercial area near the cantonment in Rawalpindi, at about 4.15 pm.

Rawalpindi police chief Rao Muhammad Iqbal said the bus belonged to the Pakistan Atomic Energy Commission (PAEC). Other officials said was it carrying over 30 employees of Khan Research Laboratories, one of Pakistan’s top strategic atomic facilities named after nuclear scientist A Q Khan.

President Asif Ali Zardari and Prime Minister Yousaf Raza Gilani condemned the attack. Zardari said “the noose around the militants had been tightened and they were acting in desperation.”