President Obama and Japanese Prime Minister Shinzo Abe address reporters after a meeting Wednesday in Ise-Shima, Japan. (Jim Watson/AFP/Getty Images)

The brutal slaying of an Okinawa woman, allegedly by a U.S. military contractor, dominated a meeting between the American and Japanese leaders Wednesday night, with President Obama expressing his “deepest regrets” to Prime Minister Shinzo Abe over the “tragedy.”

The killing has reignited outrage in the southern island prefecture over the large American military presence there, with thousands of people protesting Wednesday outside the U.S. Air Force base where the contractor worked.

“This is an unforgivable crime, and I have expressed our anger. It has shocked not just the Okinawa people but also all the people of Japan,” Abe told reporters after an hour-long meeting with Obama in Ise-Shima, ahead of the Group of Seven summit that begins Thursday. The Okinawa case took up most of the time, Abe said.

Okinawa police last week arrested Kenneth Shinzato, a 32-year-old former U.S. Marine, in connection with the killing of 20-year-old Rina Shimabukuro. Shinzato was working as a computer and electrical contractor on Kadena Air Base.

The body of Shimabukuro, who disappeared April 28, was found last week in a forest in the village of Onna, near where Shinzato told police they would find her.

Okinawa residents protest the murder of 20-year-old Rina Shimabukuro in front of the gate of Camp Foster in Kitanakagusu, Okinawa prefecture, on Sunday. (Jiji Press/AFP/Getty Images)

She appeared to have been stabbed and strangled, according to local news reports.

Shinzato, born Kenneth Franklin Gadson, took his wife’s name when he married. He has been charged with abandoning a body, a step that is often a precursor to a murder charge in Japan.

Using surprisingly strong language, the Japanese prime minister said he felt “profound resentment” at the “self-centered and absolutely despicable crime.”

“I have asked the president to carry out effective measures to prevent a recurrence of such crimes,” Abe said, a solemn-faced Obama standing beside him.

The murder threatened to dampen some of the high spirits among the Japanese public in anticipation of Obama’s historic stop in Hiroshima on Friday. Obama will become the first sitting U.S. president to visit the site where the United States dropped the world’s first atomic bomb in 1945. Administration officials said the visit will highlight the deep postwar alliance between the two nations.

On his trip to Asia, including three days in Vietnam, Obama has sought to move beyond past grievances from long-ago conflicts, promising to look to the future when he makes remarks at Hiroshima’s 30-acre Peace Memorial Park. Last week, Japanese Ambassador Kenichiro Sasae told reporters in Washington that the killing in Okinawa was a “shocking” atrocity and that the Japanese government expressed its outrage to the Obama administration.

But Sasae was careful to separate the crime from Obama’s trip to Hiroshima, where the president will be joined by Abe.

“I don’t think this should be affecting the president’s visit to Hiroshima,” Sasae said. “We have to address this [Okinawa] question . . . but it doesn’t mean that issue should be affecting in any way the meaning of the American president visiting Hiroshima.”

Anti-American sentiment was already running high in Okinawa, with sizable opposition to attempts to relocate a Marine Corps base to a new site on the island. The killing would create a new “tough and challenging road ahead,” Abe said.

At the news conference, Obama said he understood that the incident has “shaken up” people in Okinawa and across Japan.

“I want to emphasize that the United States is appalled by any violent crime that may have occurred or been carried out by any U.S personnel or U.S. contractors,” the president said. He called the slaying “inexcusable.”

Echoing Abe’s words, Obama said the United States is “committed to doing everything we can to prevent any crimes from taking place of this sort.” He suggested that Shinzato, who is in Japanese custody on Okinawa, would be tried under Japan’s justice system, even though he is covered by the Status of Forces Agreement, or SOFA, that provides the legal framework for the U.S. military presence in Japan.

Obama said the SOFA did not prevent the full prosecution and the need for justice under the Japanese legal system.

“We will be fully cooperating with the Japanese legal system in prosecuting this individual and making sure that justice is served,” he said. “We want to see a crime like this prosecuted here in the same way that we would feel horrified and want to provide a sense of justice to a victim’s family back in the United States.”

The somber nature of the news conference, held just hours after Obama landed in Japan, stood in stark contrast to the president’s visit to Vietnam, where he was feted by the leaders of the ruling Communist Party.

The slaying is stirring up memories of an incident in 1995, in which three U.S. servicemen abducted and raped a 12-year-old Okinawa girl. The case triggered huge protests and became a lightning rod for anti-American sentiment on the island chain.

About 4,000 people from citizens groups and politicians from the ruling party in the Okinawa prefectural assembly protested Wednesday near the Kadena base.

Fifield reported from Tokyo.