A baby sits in a field of flags to honor victims of the September 11, 2001 attacks, in Santa Clarita, California, September 11, 2015. REUTERS/Lucy Nicholson

CAIRO (Reuters) - Al Qaeda leader Ayman al-Zawahri called on young Muslim men in the United States and other Western countries to carry out attacks inside those countries in an audio recording posted online on Sunday.

"I call on all Muslims who can harm the countries of the crusader coalition not to hesitate," Zawahri said referring to Western nations.

"We must now focus on moving the war to the heart of the homes and cities of the crusader West and specifically America."