Hamas' armed wing says it killed 21 Israeli soldiers in Gaza

Funeral of Israeli military reservist Sergeant Major Matan Lazar in Haifa

JERUSALEM (Reuters) - The armed wing of Palestinian militant group Hamas on Tuesday claimed responsibility for a rocket attack that killed 21 Israeli soldiers in the Gaza Strip.

Israel earlier blamed unidentified Palestinian militants for the rocket-propelled grenade (RPG) attack on Monday, which was the deadliest day to date for the Israeli military in its campaign in Gaza.

"Watch the execution by Al-Qassam Brigades fighters of a compound operation against the enemy soldiers and vehicles east of the Al-Maghazi refugee camp," Hamas said in a message released to media, accompanying a video of the attack.

Israeli military spokesperson Rear Admiral Daniel Hagari told reporters in Tel Aviv that the militants' rockets hit a building where Israeli forces had laid explosives. The strike caused that building and one next to it to collapse, he said.

Most of the soldiers died there while two who were securing the area in a tank were killed by a second rocket, Hagari said, citing an initial inquiry.

The military was still studying the incident, Hagari said. Over the past 24 hours, Israeli forces killed more than 100 militants in western Khan Younis in southern Gaza, he added.

(Reporting by Maayan Lubell in Jerusalem and Nidal al Mughrabi in Doha; Editing by Cynthia Osterman and Rosalba O'Brien)