SEOUL, South Korea -- On a cold March day, the bleak monotony of a North Korean prison work detail was broken when a squad of male guards arrived and herded female prisoners together. One by one, they were asked if they were pregnant.

"They took them away in a car and then forcibly gave them abortion shots," Song Myung Hak, 33, a former prisoner, recalled recently the day two years ago when six pregnant prisoners were taken from his work unit in the Shinuiju Provincial Detention Camp. "After the miscarriage shots, the women were forced back to work."

With more and more escapees from North Korea claiming that forced abortions and infanticide are the norm in North Korean prisons, the country's official Korean Central News Agency has denounced the charges as "a whopping lie."

In 2000 and 2001, China deported thousands of North Korean refugees, with many ending up in North Korean prison camps. People who managed to escape again, to China and South Korea, say that prisoners who were found to be pregnant were routinely forced to undergo abortions. If babies were born alive, they say, guards forced prisoners to kill them.

The allegations carry special weight now as China has deported thousands more North Koreans this spring.

"Several hundred babies were killed last year in North Korean prisons," said Willy Fautre, director of Human Rights Without Frontiers, a Brussels-based private group.

"This is a systematic procedure carried out by guards and the people in charge of the prisons," Fautre said. "The pattern is to identify women who are pregnant, so the camp authorities can get rid of the babies through forced abortion, torture or very hard labor. If they give birth to a baby alive, the general policy is to let the baby die or to help the baby die with a plastic sheet."

Lee Soon Ok, who worked as an accountant during her six years at Kaechon political prison, said that twice she witnessed prison doctors killing newborns, sometimes by stepping on their necks.

With virtually no medical care available for any prisoners, surgical abortions were not an option. Lee, now 54 and an economic researcher in Seoul, said: "Giving birth in prison is 100 percent prohibited. That is why they kill those babies."

As more and more accounts of infanticide are made public by former prisoners, North Korea has issued angry denials.

On Jan. 19, North Korea's official news service said Human Rights Without Borders' charges that "unborn and newly born babies are being killed in concentration camps" were "nothing but a plot deliberately hatched by it to hurl mud" at North Korea.