Iran fired a new wave of missile attacks on Israel early Monday, triggering air raid sirens across the country as emergency services reported at least five killed and dozens more wounded in the fourth day of a conflict between the regional foes that showed no sign of slowing.

Investors have been weighing the odds of further escalation in the conflict and spillover into the broader oil-rich Middle East.

Dozens of others were injured overnight across Israel, the authorities said. Israel was striking military sites in Iran and the four-day-old conflict showed no sign of slowing.

Onlookers gathered on Saturday at a central Tel Aviv residential building next door to Israel’s defense headquarters that was damaged after it took a hit from what appeared to be shrapnel from an overnight missile barrage from Iran.

Israeli citizens were ordered to head to bomb shelters on Friday night amid retaliatory missile strikes from Iran.

Delta Air Lines Inc. and United Airlines Holdings Inc. suspended flights to Tel Aviv following Israel’s bombing of Iran and the closure of Israel’s airspace.