Egypt confirms killing of 21 Christians in Libya by IS

The victims, dressed in orange, were lined up near the seashore and forced to knee on the ground.

The Egyptians were abducted in Libya's central city of Sirte on two separate occasions in December and January, only one week apart.

Sisi said early Monday that his country reserves the right to respond at the proper time to the killing. He warned Cairo would choose the "necessary means and timing to avenge the criminal killings".

In a televised speech, Sisi said Egypt is able to defeat terrorism because "Egypt is defending humanity."

He ordered an ongoing convention of the National Defense Council, urging the government to move swiftly to assist the victims' families.

"We all need to be united to fight terrorism," Sisi said.

The Egyptian president also said that he ordered the government to enforce a travel ban to Libya.