Israel bombarded the Gaza Strip with airstrikes Monday, as it continued its response to a surprise offensive by the Palestinian militant group Hamas that began Saturday morning. Israeli ministers have ordered a “complete siege” of the already blockaded and impoverished Gaza Strip, cutting off supplies of food, water and electricity to its two million residents.

The Hamas attack, unprecedented in scale and scope, is the deadliest offensive that Israel has experienced in 50 years. Air raid sirens continue to sound in cities around Israel, while rocket strikes are reported in Tel Aviv and Jerusalem.

More than 700 Israelis have been killed in what Hamas is calling Operation Al Aqsa Flood, with at least 490 Palestinians killed in retaliatory Israeli strikes on the Gaza Strip. The total number of deaths has surpassed 1,200, including foreign nationals.

An unknown number of Israelis, both civilians and soldiers, have also been taken hostage by Hamas, prompting Israeli Prime Minister Benjamin Netanyahu to declare that his country is at war. Israel says it is working to rescue the hostages and announced it has regained control of areas outside Gaza after some 48 hours of fighting. The Israel Defense Forces said it struck more than 1000 enemy targets in overnight and daytime attacks on Gaza.

Hamas is a designated terrorist group backed by Iran and that has governed the Gaza Strip since 2007. Gaza, the small strip of land that is home to over 2 million Palestinians within roughly 140 square miles, is one of the most densely populated territories on Earth and has been kept under an Israeli land, air and sea blockade since 2007.