Officials found two packages with explosive devices on planes headed for places of Jewish worship in Chicago, President Obama said in a press conference Friday afternoon.

The packages, which were intercepted in Dubai and Britain, originated in Yemen and could have possible al-Qaida ties.

He was alerted about the "credible terrorist threat" Thursday night. Planes at the Philadelphia and Newark airports were held for additional screening Friday morning. A UPS truck in Brooklyn was also checked.

Deputy National Security Advisor of Homeland Security John Brennan spoke with the president of Yemen, who pledged full cooperation in the investigation of the packages.

Obama said he has the help of the Yemeni government to "destroy this al-Qaida affiliate."

"The American people should be confident that we will not waiver in our resolve to defeat al-Qaida and its affiliates," he said.

Reach associate news editor Taylor Freitas here. Follow her on Twitter: @taylorfreitas.

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