The Lebanese army detained a wife and daughter of Islamic State leader Abu Bakr al-Baghdadi as they crossed from Syria nine days ago, security officials said yesterday, in a move seen as likely to put pressure on the Islamist chief.

The woman was identified as Saja al-Dulaimi, an Iraqi, by a Lebanese security official and a senior political source.

The Lebanese newspaper As-Safir reported she had been detained in coordination with “foreign intelligence”.

A Lebanese security source said the arrest was “a powerful card to apply pressure” in negotiations to secure the release of 27 members of the Lebanese security forces captured by Islamic militants – a view shared by other Lebanese officials who confirmed the arrest.

A senior Lebanese security official said al-Baghdadi’s wife had been travelling with one of their daughters, contradicting earlier reports that it was his son. DNA tests were conducted to verify it was al-Baghdadi’s child, the official said.

They were detained in northern Lebanon. Investigators were questioning her at the Lebanese Defence Ministry.

US officials said they were looking into the reports from Lebanon. One official said that if one of al-Baghdadi’s wives or children were detained, the US believes it could positively identify them, though the official would not say how.

Fawaz Gerges, a Middle East expert at the London School of Economics, said the arrest indicated that the American-led coalition seemed to have solid intelligence in Syria and Iraq.“I talked to a few people who told me this was a coordinated arrest between American intelligence services and the Lebanese army,” he told Reuters.

“If I were Abu Bakr al-Baghdadi, I would be very anxious that they are getting very close,” he said. “This is a development ... that is very alarming for Isis, in particular the top leadership.”

Dulaimi was one of 150 women released from a Syrian government jail in March as part of a prisoner swap that led to the release of 13 nuns taken captive by al-Qaeda-linked militants in Syria, according to media reports at the time.

Al-Baghdadi has three wives, two Iraqis and one Syrian, according to tribal sources in Iraq.

The United States is offering $10 million for information on al-Baghdadi, an Iraqi, whose real name is Ibrahim Awwad Ibrahim Ali al-Badri al-Samarai.