Two car bombs have exploded in the Pakistani city of Karachi, killing a policeman and injuring at least 25 other people, police said.
The car bombs went off 200 metres from the US consulate
One car exploded outside an English language school and minutes later a second parked nearby blew up.
The explosions come a day after another blast in the southern port which killed two people and injured two more.
Wednesday's attack occurred 100 metres from the US consul-general's home and 200 metres from the old US consulate.
Security at the port had been tightened after Tuesday's attack, with extra police searching vehicles.
A police office told the AFP news agency that Wednesday's first car bomb was followed by a "more severe" second blast.
At least 25 people are reported to have been injured, including about 10 journalists and a number of senior policemen.
The explosions were between 15 and 30 minutes apart.
The BBC's Paul Anderson in Islamabad says the first car had a government licence plate and did not immediately arouse suspicion.
Police sealed off the area after the first blast and bomb experts were inspecting the wreckage when the second car exploded.
It damaged the outer wall of the Pakistan-American Cultural Centre, in which Pakistani students were taking English language classes at the time.
Police have also been checking a third suspect car.
A Reuters correspondent said: "There was a loud explosion and we were all stunned. Debris... hit people and I saw people with head cuts and blood coming from their arms and legs."
The injured were taken to two hospitals in Karachi. Television pictures showed casualties filling one ward.
It is not clear who carried out any of the attacks.
Pakistan's information minister, Sheikh Rashid Ahmed, condemned the bombings, blaming "enemies of Pakistan".
"We are playing a front-line role in the war against terrorism and terrorists are of course not happy," he said.
Karachi is Pakistan's biggest port and is a centre of activity for extremist groups.
In March, police said they defused a huge bomb in a van parked outside the US consulate in Karachi.
However, experts later cast doubt on whether the chemicals found were inflammable or explosive.
A suicide bomber killed 12 people, all Pakistanis, outside the US consulate in the city in June 2002.
A month earlier, a suicide bomb attack outside Karachi's Sheraton hotel killed 11 French naval engineers helping Pakistan's navy develop a new submarine.