Festivalgoers, children, soldiers: What we know about the people captured by Hamas

Dozens of people are believed to have been captured in Israel by Hamas fighters over the weekend. They are now being held in locations across Gaza, complicating Israel's response to the militant group's deadly attack on Saturday.

Israel is taking pains to establish the exact number of hostages that have been taken into Gaza, an isolated coastal enclave of almost 2 million people crammed into 140 square miles, one of the most densely populated places in the world.

Lt. Col. Richard Hecht, the military's international spokesperson, told CNN on Sunday that "dozens" had been captured and emphasized just how complex the situation was as the army launched air strikes on Gaza in retaliation. In an earlier briefing he had said "civilians, children and grandmothers" were among those being held captive.

In addition to Israeli captives, there are several other nationalities believed to be taken hostage.

Al Qassam Brigades, the armed wing of Hamas, has warned that Israeli attacks in the area could pose a threat to hostages, with its spokesman, Abu Obaida, saying in a recorded audio message Saturday that they were "present in all axes in the Gaza Strip."

Lt. Col. Jonathan Conricus, an Israel Defense Forces (IDF) spokesperson, told CNN's Wolf Blitzer that "it is unprecedented in our history that we have so many Israeli nationals in the hands of a terrorist organization."

It has been more than 17 years since an Israeli soldier was taken as a prisoner of war in an assault on Israeli territory. And Israel has not seen this kind of infiltration of military bases, towns and kibbutzim since town-by-town fighting in the 1948 war of independence.