She said the UN mission, Monusco, had reported new attacks in the Walikale region where militias and Rwandan rebels and raped hundreds of women in front of their villages and families earlier this year. This time the attacks are coming from the DRC’s army, FARDC.
"I am gravely concerned about the ongoing military operations by FARDC in the Walikale territory and the implications for the protection of civilians," she told the UN Security Council on Thursday.
"There is already some information from Monusco peacekeepers on the ground that rapes, killings and lootings have been perpetrated by FARDC soldiers. The possibility that the same communities that were brutalised in July and August by FDLR and Mai-Mai elements are now also suffering exactions at the hands of FARDC troops is unimaginable and unacceptable."
Wallstrom said the Security Council should escalate the focus of the DR Congo sanctions committee on sexual crimes.
Rwandan liberation militia leader Lieutenant Colonel Seraphim of the FDLR should face international sanctions, she said, alleging that he was also to blame for the mass rapes in July and August.
A Mai-Mai leader, Lieutenant Colonel Mayele, was arrested in an operation by Indian peacekeepers with the Monusco mission on 5 October after he was handed over to authorities by members of his own group.
Wallstrom said Mayele’s arrest was an important precedent.
"When commanders can no longer rest easy in the certainty of impunity, when it begins to cross their mind that they may be turned in by their own, for commissioning or condoning rape, this is the moment when we open a new front in the battle to end impunity," she said.
UN peacekeepers in DR Congo are "overstretched and under-resourced", Wallstrom added.
"They are demoralised by the sheer scale of the problems and constant barrage of criticism from all quarters," she said.
Monusco has about 20,000 staff and troops from more than 50 countries and costs more than 900 million euros a year.