Senior police officials denied media reports the suspect was planning to assassinate Prime Minister Zafarullah Khan Jamali (search), who is currently visiting Karachi — a city hit by a wave of terrorist attacks in recent years.
A member of the outlawed Jaish-e-Mohammed militant group is in police custody, said Faisal Noor, a senior Karachi police officer.
"We did arrest this person. We also seized explosive material and three hand grenades from his place but he had no plan to kill Prime Minister Jamali," Noor told The Associated Press.
He said that police found 19 locally made time bombs at the suspect's house.
Noor identified the suspect as Naeem Rahmani and said he was still being interrogated.
Chief of Sindh province police Syed Kamal Shah and Jamali's spokesman Majeed Niazi also denied there had been any assassination attempt.
Niazi said the prime minister was in Karachi on a visit and would return to the capital Islamabad on Thursday evening.
Karachi, a southern port city of 14 million, has suffered a series of attacks by Islamic extremists in recent years.
On March 15 this year, police defused a huge bomb outside the U.S. Consulate in Karachi, minutes before it was timed to explode. Police have not publicized the arrests of any suspects.
In June 2002, a suicide bomber blew up a truck in front of the consulate, killing 14 Pakistanis.
In April 2002, a bomb aimed at the motorcade Pakistan's President Gen. Pervez Musharraf, a key ally in the U.S. ally in the war on terrorism, failed to detonate as he traveled through Karachi. Three Islamic militants were sentenced to 10 years in prison in that attempt.