ZAGREB, Croatia (AP) _ The Serbian fighters who have seized large parts of Bosnia-Herzegovina are being accused of systematic rape against captured Muslim women and girls.

The accusations, by Bosnian officials, foreign activists and by the alleged victims themselves, have mounted along with reports of murders, beatings and forced relocations of civilians in the war-torn country.

Bosnian Serb spokesmen have dismissed the rape reports as fabrications. But there have been dramatic accounts of the alleged assaults, particularly this month on television in Croatia, a former republic of Yugoslavia that has fought its own bitter war against Serbia.

In one account, Vazima Visovic, a slender, 12-year-old Muslim girl, described her ordeal last summer in a Serbian camp for women in Foca, southern Bosnia.

''We were kept there for 27 days and got almost nothing to eat. The Chetniks beat us, abused us and raped us, including me,'' she said, her stony voice sounding agonizingly adult.

''They were coming night and day, always in groups of two or three, and took us to apartments - me, my mother and another woman. One man raped all three of us. ... I was always raped by two or three.''

Asja Kesma, 22, from Visegrad on Bosnia's eastern border with Serbia, said the rapes started after Serbs killed her husband in August. She said she was raped by 17 men over four days, including one night by 12 men.

''Lots of women went ... to have an abortion,'' she said in the Dec. 5 Croatian TV report. ''If I was pregnant, I would drown the infant immediately after its birth with my own hands.''

Croatian and Sarajevo TV have broadcast reports hostile to Serbs, and Serbian TV has aired similar reports against Croats and Muslims, reflecting the bitterness between the ethnic groups. However, accounts of rape in Bosnia from other victims lend credence to the TV interviews.

The Associated Press this month interviewed a blonde 17-year-old from Tesanj in central Bosnia who said she and her mother were raped at their home by Serbs after her father and brother had gone into hiding.

She said the attackers left her mother but took her to a camp in the woods with 11 other women. After three months she said she escaped with a guard's help.

The girl, who was nearly six months pregnant and didn't want her name used, was interviewed in a Zagreb hospital.

Europeans, especially Germans who have asked the European Community for an investigation and help for the Muslim victims, have expressed outrage over the rape allegations.

''Testimony from maltreated women and girls points to the existence of at least 16 specially equipped locations ... in which women were held and abused,'' German Foreign Minister Klaus Kinkel said in a Dec. 2 letter to his British counterpart, Douglas Hurd.

Demonstrations have been held outside the Yugoslav embassy in Bonn.

In Switzerland, thousands of people took part in marches, vigils and human chains Thursday night, demanding sexual torture be included in the Geneva conventions as a war crime.

A captured Bosnian Serb soldier told The AP in Sarajevo two weeks ago of being ordered by superiors to rape and kill two young Muslim women at a prison-brothel on the city's outskirts.

''If I didn't kill them, I would be shot,'' said Borislav Herak. ''And they said I had to rape them, that it was important for a soldier's morale.''

Raimar Wigger, field coordinator in Zagreb for the German ''Cap Anamur'' Emergency Doctors Committee, said the various accounts add up to organized rape and forced pregnancy as a weapon of ethnic conflict.

''A lot of these women are girls, children even, 12 years old. Some are pregnant being 16, and if they have the babies they don't know where they are going to be able to take care of them,'' Wigger said.

''These girls and women are completely helpless. Thousands of them are still in these bordello camps,'' he said.

In Geneva, Bosnian Serb leader Radovan Karadzic denied Friday that his forces are involved in organized rape. He charged that Muslims in Sarajevo have kept Serbian women for their own soldiers.

''Whatever they do, they accuse us of doing,'' Karadzic asserted.

The Bosnian government vehemently denies such allegations.

The German doctors, the Red Crescent Society and the Zagreb Women's Autonomous House are among organizations scrambling to establish shelters for Bosnian women victims.

No one knows how many women were raped. Bosnian Foreign Minister Haris Silajdzic, speaking to reporters in Geneva on Thursday, estimated 14,000 to 30,000 victims of rape.

Izet Aganovic, president of Merhamet, or the Red Crescent, in Zagreb, said he saw many rape victim among the 100,000 people who have camped at a Zagreb mosque awaiting refugee housing.

Muslim religious leaders are trying to convey to the highly patriarchal society that they are to be accepted back by their husbands and young men as guiltless victims, Aganovic said.

After giving birth, he said, the women will be asked to decide whether they can accept the children or want to give them up for adoption.