The Lebanese army detained a wife and a son of ISIS leader Abu Bakr al-Baghdadi as they crossed from Syria in recent days, security officials said on Tuesday.
The officials declined to give the name or nationality of the woman whom they described as one of his wives. The Lebanese newspaper As-Safir reported the army had detained her in coordination with "foreign intelligence apparatus".
It said she had been travelling with a fake passport accompanied by one of her sons. ISIS has seized wide areas of Iraq and Syria, Lebanon's neighbour to the east, declaring a self-proclaimed "caliphate" over the territory it controls.
Investigators were questioning her at the headquarters of the Lebanese defence ministry, As-Safir reported.
The Lebanese security forces have waged a crackdown on ISIS sympathisers in Lebanon and the intelligence services have been extra vigilant on the border crossings.
They have arrested over the past few months a number of militants suspected of staging attacks to expand ISIS influence in the country neighbouring Syria.
A U.S.-led alliance is seeking to roll back ISIS's territorial gains in Iraq and Syria. U.S. President Barack Obama has vowed to "degrade and ultimately destroy" Baghdadi's group, which is seeking to reshape the Middle East according to its radical vision.
Baghdadi, an Iraqi, called for attacks against the rulers of Saudi Arabia in a speech purported to be in his name last month.
He said his self-declared caliphate was expanding in Saudi Arabia and four other Arab countries and called for "volcanoes of jihad" the world over in the speech released on Nov. 13.