Officials in Germany solemnly commemorated the liberation of two Nazi concentration camps 70 years ago in the closing days of World War II.

Poland's first lady, Anna Komorowska, joined in remembrance activities Sunday at the site of the Ravensbrueck women's camp in northern Germany. Many of the prisoners came from Poland.

Komorowska, wife of Polish President Bronislaw Komorowski, planted a memorial rose along with Daniela Schadt, partner of German President Joachim Gauck, and camp survivor Annette Chalut.

Elderly survivors joined black-clad Polish nuns, some of whom held red and white Polish flags. A Mass was said in Polish.

Ceremonies have been held across Germany and Poland throughout the spring marking the advance of Allied troops as Nazi Germany neared defeat. They are even more poignant this year because of the dwindling number of survivors and witnesses to the Holocaust, the murder of 6 million Jews by the racist and anti-Semitic regime of German dictator Adolf Hitler.

Ceremonies also were taking place at the former Sachsenhausen camp near Berlin.

The U.S. Holocaust Memorial Museum says 30,000 to 50,000 people died at Sachsenhausen, where inmates included Jews, Poles, Soviet prisoners of war and opponents of the Nazis.

At Ravensbrueck, more than 130,000 women passed through the camp and 20,000 to 30,000 died there. Inmates were subjected to forced labor in the armaments industry. Many died because of malnutrition and disease in filthy conditions; thousands of others were shot or sent to gas chambers if considered too weak or injured to work.

Days before Allied troops arrived, Nazi officials forced thousands from the camps to start death marches away from the camps. Many of those prisoners died of exposure or disease or were killed by guards along the way. Sachsenhausen was liberated by Polish troops under Soviet command on April 22, 1945, Ravensbrueck by Soviet forces on April 30.