Ehud Barak, the political rival of outgoing Prime Minister Benjamin Netanyahu, was in office in 2000 when security forces killed 13 people during violent “Land Day” demonstrations.

“Land Day” commemorates each year the deaths of several Arabs killed in 1976 during an altercation with Israel

Israeli Arab MP Esawi Frej called on Barak to apologize and take responsibility for the deaths. Earlier this month, Frej, of the left-wing Meretz, ruled out any alliance with Ehud Barak’s party, “Democratic Israel,” ahead of the September general election because of the 2000 killings.

Esawi Frej’s words “come from deep pain,” Ehud Barak told Israeli public radio.

“These are important and painful things. I take responsibility for everything that went right or wrong during my tenure as Prime Minister, including the events of October 2000 in which 12 Israeli Arabs and a Palestinian from Gaza were killed,” he said.

“I repeat my regrets and apologies to the families of the victims,” he added.

Barak who headed the Labor party defeated Netanyahu in the 1999 general elections. However, his government was short-lived after being defeated in the 2001 general elections by Ariel Sharon.

Barak returned to the Labor Party in 2005, and in 2007 was appointed Defense Minister by then-Prime Minister Ehud Olmert. He actually continued serving in that position until 2013 while Netanyahu was prime minister.

The 77-year-old former lieutenant general was the most decorated Israeli soldier and longest-serving chief of staff of the Israel Defense Forces before assuming the position of Prime Minister in 1999.