Israeli airstrikes continued to pound Beirut on Saturday after Iran’s supreme leader declared the country’s allies won’t back down in a war in West Asia that threatens severe global ramifications. The strikes came a day after Israel killed Hezbollah leader Hassan Nasrallah, inflicting a blow to the group, which is fighting to preserve its territory in Lebanon. The escalation also prompted the United States to warn that it would respond with greater force.

The latest strikes hit the affluent Bachoura neighborhood, targeting a building near the Lebanese parliament. A loud explosion shook the capital and left the first floor of the apartment building partially destroyed. Hezbollah members reportedly used the building for underground meetings.

Israel has targeted more than 200 Hezbollah targets since Monday, including weapons depots and missile platforms. It said it would continue “to disrupt terrorist elements in Hezbollah’s operational infrastructure and to degrade their capabilities.”

One of the targets was a tunnel under an area of central Beirut known as Dahiyeh, which gave rise to Israel’s infamous “Dahiyeh doctrine.” A tunnel beneath that neighborhood allows Hezbollah fighters to smuggle weapons from Iran into Lebanon. The strikes were part of a campaign to eliminate Hezbollah’s military commanders, who are responsible for security along the contested border between Lebanon and Israel. Israel has claimed it has killed several such officers but hasn’t released their names.

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In addition to the tunnels, the airstrikes hit a mosque near a hospital and other civilian facilities. The Salah Ghandour Hospital reported that nine of its staff were wounded, most seriously. An Israeli official said air defense fighters intercepted some rockets.

The strike on the mosque was a violation of a ceasefire, and a Lebanese government official demanded an explanation from Israel. The official, Najwa al-Waleedi, described the strike as “an aggression against all Lebanese and Arab communities.”

Another airstrike reportedly struck a warehouse in the southern town of Quneitra that housed Hezbollah’s missile assembly plant. The blast caused extensive damage to the facility, and a video emerged showing the smoldering wreckage of the building.

Israel’s campaign has displaced thousands of people, and more than 900 centers set up to shelter them are complete, Lebanese Prime Minister Najib Mikati said. The displaced include many children.

The Biden administration’s months long effort to avoid a full-scale war between Israel and Iran faces its biggest test yet. Top officials in the administration, however, are still urging restraint, and they worry that a more aggressive response from Israel could derail talks on a comprehensive peace plan with Hezbollah and Syria. The United States and its allies are prepared to respond more forcefully, but they hope diplomacy can save the situation from further deterioration.