'These are the first Rwandans to cross today,' said the young Burundian woman at the border post. 'We let them in, but we can't help them. Can you take them to hospital?'
Aid workers drove the injured couple to the tiny provincial hospital at Kayanza, where local staff and the Red Cross are struggling to treat 450 seriously wounded and sick refugees. Most of the injured, including children, have machete, bullet or grenade wounds. Medical teams say many have had their fingers sliced off, or been hacked in the back of the neck.
Three weeks after the plane crash that killed the presidents of Rwanda and Burundi and triggered violence throughout Rwanda, refugees and the last few foreigners to leave the country tell stories of unceasing horror. Bands of young men mad with killing, some with banana fronds tied around their heads as masks, are burning villages and murdering tens of thousands of people.
Refugees arriving in Burundi say bodies are piled high at arbitrary checkpoints on the road south out of Rwanda's second city, Butare, and that the number of people crossing the border is small compared to those killed on the way. The International Committee of the Red Cross, says 100,000 or more people are dead.
The refugees are from the region's minority Tutsi tribe. They say that the massacres are carried out by militia known as 'Inherahamwe', who are drawn from the majority Hutu tribe, and taking orders from the military, police and local government officials known as 'Bourgmestres'. Foreigners who have lived in Rwanda for decades confirm that the Bourgmestres and eminent local Hutus are behind the killings.
'They're killing all the Tutsis,' said Antime Gusana, a teacher from Runyinya, west of Butare, who fled into Burundi with his wife and four children. 'We hid high up in the hills, but they chased us out. The police and armed gangs came for us with grenades and guns. I saw the local brigadier and even the Bourgmestre among them.'
Although Rwanda has had a Hutu-dominated government since independence, Tutsis, the traditional aristocracy of the region, remain a social elite. Politicians and the military are able to manipulate Hutu peasants, whose resentment of the Tutsis has smouldered for years.
The UN High Commissioner for Refugees says that 40,000 Rwandans have managed to cross the border into Burundi. On Friday, 250,000 Rwandans poured into Tanzania in the fastest exodus UNHCR staff have ever seen.
'I fear we won't see a lot more coming now,' said Maurice Herson of Oxfam. 'I think it's unlikely that many more will have survived the violence. In addition, people have been hiding for nearly three weeks, probably without food or shelter, so the chances of many surviving that are slim.'
Oxfam has described the killings in Rwanda as genocide. Hutu politicians opposed to the late president Juvenal Habyarimana were targeted in the first few days after the plane crash, which has yet to be satisfactorily explained. But now the killings seem to be directed purely against Tutsis. Rwanda's Tutsi population is estimated at about 800,000.
In the Rwandan capital, Kigali, fighting between government troops and rebels of the Rwanda Patriotic Front continues, despite UN efforts to arrange a ceasefire. The RPF, a largely Tutsi force that was based near the border with Uganda, is reported to control much of northern Rwanda and part of the capital, Kigali.
Rwandan government radio is blaming the RPF for the massacres, though the RPF has not reached the south where many of the atrocities are being committed. Eye-witnesses report that the RPF has killed civilians in Kigali, but the rebels say that they are targeting only Inherahamwe.
The authorities in Burundi are welcoming Rwandan refugees, but fear violence will spill over the border. Burundi has the same ethnic mix as Rwanda, and an even bloodier history of coups and massacres. The army has always been dominated by Tutsis, and until last June's election of a Hutu president, Melchior Ndadaye, the Hutu majority had no power.
Last October a failed coup, in which President Ndadaye was assassinated, unleashed a wave of ethnic killings in the countryside. Tutsis gathered in camps inside Burundi, protected by the army, while more than half a million Hutus fled to Zaire, Tanzania and Rwanda.
The violence in Rwanda has driven about 150,000 Burundian Hutu refugees back over the border in the past three weeks. Many are still afraid to return to their homes, so they have gathered in camps - refugees in their own country.
Burundi's politicians have to tread a careful line between the Tutsi army, whose co-operation they need to prevent a coup, and their mass of Hutu supporters. On Thursday night, the army shelled the suburb of Kamenge in the north of the capital, where Hutu extremists had been resisting the military's attempts to disarm them. Several thousand civilians who had been trapped in Kamenge managed to flee, and are now staying in a makeshift camp in a sports stadium in the centre of Bujumbura.