ISLAMABAD, Pakistan, March 16— Preying on this nation's pervasive poverty, a kidnapping gang, including three nurses, has been buying children from desperately poor parents, and then smuggling them to Malta where they are resold at a substantial profit, police authorities said today.

On Friday, the police in the port city of Karachi found 11 children, ranging in age from 2 weeks to 2 years, in a small room where they slept on a dirty mattress, and arrested eight people -- three Maltese and five Pakistanis -- on suspicion of trafficking in children.

In a grim reflection of the gang's motives, the children were described as being in ''perfect condition,'' said Faisal Edhi, whose family foundation runs one of the largest charities and orphanages in Pakistan. ''If somebody wants to sell his commodity, it must be in good condition.''

The suspects had 13 false passports and false birth certificates, the police said. They also had adoption papers, with official Maltese government stamps, which the police said had been supplied by the wife of the gang leader, who lives in Malta.

''We do not feel this is the first time they have done it,'' Fayyaz Leghari, the chief police investigator in Karachi, said in a telephone interview today. ''They have this whole racket going on.''

Four years ago, the man who is suspected of being the gang leader was arrested on suspicion of trying to smuggle six children. He jumped bail and disappeared until his arrest on Friday.

In Pakistan, where the crime rate is as high as law enforcement is weak, it is unlikely that the authorities will ever get a full picture of the extent of trafficking in children.

The police said they did not know where the 11 children found on Friday came from. The suspects have told the police that they had found the children abandoned outside Christian churches, and that they were taking them to give to couples abroad who wanted to adopt.

The police say the children may have been kidnapped, taken from hospitals where they had been abandoned by parents too poor to care for them, or bought from parents.

The root of the trafficking is poverty, said Mr. Edhi. ''Here people are too poor, so they need money and they sell their children,'' he said.

One market for children is the Middle East. Young boys are sold by their families for use there as jockeys in camel races.