JERUSALEM - Israel carried out airstrikes in the Gaza Strip, killing at least 20 people, as rocket fire from the Palestinian enclave continued through Monday night, according to Israeli and Palestinian sources.

After hundreds of Palestinians were injured in clashes with Israeli police in East Jerusalem on Monday morning, Hamas launched a rocket attack at Jerusalem in the afternoon, which drew a heavy Israeli response.

An Israeli military spokesperson said in a statement that fighter jets struck an offensive tunnel belonging to Hamas. According to Israeli media, several militants inside the tunnel were killed in the attack.

The Israeli air force struck additional sites belonging to Hamas including two rocket launchers and two military posts.

The Hamas-run health ministry in the Gaza Strip said in a statement that 20 people were killed, including nine children, and 65 others wounded on Monday evening in explosions in the town of Beit Hanoun, northern Gaza Strip.

The sharp escalation began at 6 p.m. (15 GMT) after Hamas set an ultimatum for Israel to withdraw its forces from the Al-Aqsa Mosque compound in East Jerusalem, where Israeli police injured hundreds of Palestinians in clashes earlier on Monday.

After the deadline, Hamas launched seven rockets at Jerusalem, according to the Israeli army. One of them caused a light damage to a home.

Over 100 rockets have been fired at southern Israel since the afternoon, lightly injuring two people. A third person was lightly injured by the remanent of an anti-rocket Iron Dome interceptor missile.

The Israeli army said in a statement that dozens of the rockets were intercepted by the Iron Dome system.

Israeli Prime Minister Benjamin Netanyahu accused Hamas of "crossing a red line" with the rockets on Jerusalem, and vowed that "Israel will respond with great forcefully."

The military's Home Front Command said the schools have been canceled in communities in the vicinity of the Gaza Strip and instructed residents to stay indoors.

The Israeli Airports Authority said that landing routes were redirected to avoid possible harm.