JERUSALEM (AP) — A Syrian anti-aircraft missile landed in southern Israel early Thursday, setting off air raid sirens near the country's top-secret nuclear reactor, the Israeli military said. In response, it said it attacked the missile launcher and air-defense systems in neighboring Syria.

It marked one of the most serious incidents of violence between Israel and Syria in years. However, Israeli media later described the Syrian missile as an “errant” projectile, not a deliberate attack deep inside Israel.

Syria's state news agency SANA said the exchange began with an Israeli air strike on Dumeir, a suburb of the capital of Damascus. Dumeir is believed to house Syrian army installations and batteries as well as bases and weapons depots belonging to Iran-backed militias. SANA said four soldiers were wounded.

The Britain-based Syrian Observatory for Human Rights, an opposition war monitoring group based in Britain that tracks Syria’s civil war, said the Israeli strikes hit an air defense base belonging to the Syrian military and destroyed air defense batteries in the area. It said the Syrian military fired surface-to-air missiles in response.

Syrian media made no mention of an anti-aircraft missile landing deep inside Israel.

The Israeli military described the projectile that landed near the nuclear site as a surface-to-air missile, which is usually used for air defense against warplanes or other missiles. That could suggest the Syrian missile had targeted Israeli warplanes but missed and flew off errantly. However, Dimona, the Negev desert town where Israel's nuclear reactor is located, is some 300 kilometers (185 miles) south of Damascus, a long range for an errantly fired surface-to-air missile.

The Israeli army said it had deployed a missile defense system but could not confirm if the incoming missile was intercepted, though it said there had been no damage. The air raid sirens were sounded in Abu Krinat, a village just a few kilometers (miles) from Dimona. Explosions heard across Israel might have been the air-defense systems.

The military said that in response to the incoming missile, it launched an air strike at the battery that launched the anti-aircraft missile and other surface-to-air batteries in Syria.

The exchange between Israel and Syria comes against the backdrop of growing tensions between Israel and Iran, a key ally of Syria. Iran, which maintains troops and proxies in Syria, has accused Israel of a series of attacks on its nuclear facilities, including sabotage at its Natanz nuclear facility on April 11, and vowed revenge. It also threatened to complicate U.S.-led attempts to revive the international nuclear deal with Iran.

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Associated Press writer Jon Gambrell in Dubai, United Arab Emirates, contributed to this report.