TV footage showed what looked like Israeli interceptor missiles streaking into the sky above Tel Aviv, Israel’s commercial capital, and detonating.
Explosions rang out, but there were no reports of injuries or damage. Despite the apparent activation of Israel’s Iron Dome air defense system, the military said no rockets were shot down.
“No rocket fell in any built-up area,” military spokesman Brigadier-General Ronen Manelis told Israel Radio, declining to provide further operational details.
It was the first time sirens had rung out in the city since the 2014 Gaza war between the territory’s dominant Hamas Islamists and Israel. There have been several smaller rounds of fighting since, reined in by Egyptian and U.N. mediations.
There was no claim of responsibility in the Gaza Strip, where Hamas was engaged on Thursday in talks with Egypt on a long-term ceasefire with Israel.
“This was basically a surprise,” Manelis said, adding that Israel had no advance intelligence warnings of the rocket fire.
“We don’t know who carried it out (but) the Hamas organization is the main organization in the Strip. It is responsible for what happens within the Strip and what emanates from it.”
Hamas did not immediately respond. Islamic Jihad, a smaller yet well-armed Palestinian faction, denied firing any rockets.
About 40 minutes after the alarm went up, traffic was flowing normally on Tel Aviv’s main Ayalon highway. Still, the municipality asked residents to open up bomb shelters as a precaution.
Israeli Prime Minister Benjamin Netanyahu’s office said he was conferring with senior military and security staff.
Any escalation in fighting could tilt Israeli public opinion ahead of an April 9 election that Netanyahu is contesting.
Tensions have been high for the past year along the Israel-Gaza frontier since Palestinians began violent protests near Israel’s border fence that have often drawn a lethal response from the Israeli military.
The rocket fire raised speculation in Israel that Palestinian militants opposed to any deal between Hamas and Israel were behind the launchings.
Israeli Finance Minister Moshe Kahalon said on Twitter that Israel “would respond as necessary” to the rocket attack.
The anniversary of the Gaza border protests is in two weeks, on March 30 and Palestinian groups have been preparing events and march to mark the date.
Around 200 Palestinians have been killed in the demonstrations and about 60 other Palestinians have died in other incidents, including exchanges of fire across the border.
Since the protests began, one Israeli soldier was shot dead by a Palestinian sniper along the frontier and another was killed during an undercover raid into Gaza.
Fires caused by Palestinian incendiary devices attached to kites and balloons have set ablaze large areas of Israeli forest and farmland along the Israel-Gaza border.