Jerusalem ? A gunman walked into a prominent Jewish seminary in Jerusalem on Thursday evening and opened fire on students as they read in the library, killing eight and wounding nine in one of the deadliest attacks on Israeli civilians in years.

Witnesses said students at the Mercaz HaRav yeshiva, a stone and glass structure set on a quiet residential street, initially thought the noise of gunshots was from firecrackers set off to celebrate the first day of Adar, a month for rejoicing in the Jewish calendar.

The attacker fired dozens, perhaps hundreds of rounds, witnesses said, before he was killed by an Israeli army officer who rushed into the school after hearing the shots.

The attack was likely to further strain a faltering U.S.-backed peace process, days after more than 120 Palestinians, many of them civilians, were killed during an Israeli offensive in the Gaza Strip. President Bush has encouraged the two sides to reach a peace agreement by the end of his term in office; Secretary of State Condoleezza Rice visited the region this week in an effort to keep the talks on track.

A television station operated by Hezbollah, the Lebanese Shiite movement backed by Syria, said a previously unknown group asserted responsibility for the attack. The group is named in part for Imad Mughniyah, a Hezbollah leader killed in Damascus last month in a car bombing the group blamed on Israel, a charge Israeli officials denied.

Hamas, the radical Islamic movement that controls Gaza, praised the attack. “It was a natural response to Israeli crimes in Gaza,” the organization said in a statement. “We bless this act. It won’t be the last one.” Thousands of Palestinians in Gaza City celebrated in the streets, firing guns into the air in jubilation, as word began to spread.

Israel blamed the assault on Islamic extremist groups, saying that the same people responsible for firing rockets toward Israeli towns bordering Gaza were also to blame for Thursday night’s killings.

“Tonight’s massacre is a defining moment,” said Mark Regev, spokesman for Israeli Prime Minister Ehud Olmert. “The people celebrating have exposed themselves for what they really are: hateful extremists.”

Bush called Olmert to express his condolences and issued a statement saying that “this barbaric and vicious attack on innocent civilians deserves the condemnation of every nation.”

Palestinian Authority President Mahmoud Abbas, Israel’s partner in peace talks, also condemned the killings.

Israeli media quoted security sources as saying they believed the gunman was a young Palestinian man who lived in East Jerusalem.

Mercaz HaRav is considered a wellspring of religious Zionism, the movement that has motivated many Jews to settle the West Bank following Israel’s seizure of Palestinian territories in 1967. Israel withdraw its soldiers and settlers from Gaza in 2005.

The eight people killed were rabbinical students in their late teens or 20s, police said.

The attack shook residents of Jerusalem, which has not experienced an attack of similar magnitude since 2004. Within minutes of Thursday’s killings, people who had been out at restaurants and bars began anxiously huddling around television sets and radios to get the latest news.