CAIRO, Feb 16 (Aswat Masriya) - The Egyptian air force has launched a fresh round of strikes against militant targets in the Libyan city of Derna, in coordination with Libyan armed forces on Monday afternoon, a military source said.

Egypt's air force had launched a first round of airstrikes at dawn after a video surfaced showing the beheadings of 21 Egyptian nationals in Libya.

The military source told Aswat Masriya that military ground operations on Libyan soil are unlikely. He added that the Egyptian airforce will carry out "preventive strikes" near Egypt's borders with Libya.

Egypt's army said the targets of the strikes are "training points and weapons and ammunition storage" sites belonging to the Islamic State fighters in Iraq and Syria, on Libyan soil.

Libyan Air Force Chief of Staff Sakr al-Joroushi told Aswat Masriya that the dawn airstrikes have left no less than 50 militants killed.

Following the first airstrikes, Islamist militant group Fajr Libya or Libya Dawn called on Egyptians in Libya to leave within a maximum of 48 hours "for their own safety". The militant group has gained control over Libyan capital Tripoli since August 2014.

Late on Sunday, a video titled "a message signed with blood to the nation of the cross" surfaced. It showed masked men beheading 21 Egyptian Copts who had been kidnapped in Libya for weeks.

The men responsible for the beheading are believed to belong to a division of Islamic State Fighters in Libya.

In response, President Abdel Fattah al-Sisi said in a televised address that "Egypt reserves the right to respond in the method and timing it deems suitable for retribution from these killers."