The sirens sounded on Thursday in the Israeli district of Abu Qrenat, near the Dimona nuclear reactor, the Israeli army said on Thursday without immediately providing further details.
A Reuters reporter about 90 km away heard the sound of an explosion a few minutes before the army’s military message.
Such siren alerts are generally triggered by missile attacks.
Israeli Army Radio said that if such an attack had taken place early Thursday, its origin was not immediately clear.
Abu Qrenat is deeper into Israeli territory than the usual range of missiles from Palestinian militants in the Gaza Strip.
Israeli media have been saying for weeks that air defense in the Dimona area and the Red Sea port of Eilat has been strengthened in anticipation of a possible long-range missile or drone attack by Iranian-backed forces – perhaps even from Yemen.
Tensions are high between Israel and Iran over the Tehran nuclear program and a recent rise in sabotage attacks, some of which have blamed each other.
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