UN leader Ban Ki-moon is "outraged" at the killing of seven Tanzanian peacekeepers in an ambush in Darfur and called on the Sudanese government to take action, his spokesman said Saturday.

The seven were killed by unidentified attackers near Nyala in South Darfur. It was the latest of a series of attacks on UN troops in the western region this year. No perpetrators have yet been caught.

"The secretary general was outraged to learn of a deadly attack on peacekeepers in Darfur which occurred this morning," said UN spokesman Martin Nesirky.

"Seven Tanzanian peacekeepers were killed and 17 others are injured. Among the injured are four UNAMID police officers, including two female officers, and 13 troops," the spokesman added.

Ban sent "deepest sympathies" to the families of the dead and the Tanzanian government, a major contributor to the UN-African Union force in Darfur.

"The secretary general condemns this heinous attack on UNAMID, the third in three weeks, and expects that the government of Sudan will take swift action to bring the perpetrators to justice."

UNAMID has more than 19,500 troops and police in the region where the UN says an armed uprising against the government that started a decade ago has left more than 300,000 dead.