The Egyptian Government has welcomed Saudi Arabia's decision to classify the Muslim Brotherhood as a terrorist organisation, and called on other Muslim countries to follow suit.
The Saudi decision to blacklist the Brotherhood further isolates the party of the deposed Egyptian president Mohamed Morsi.
Saudi Arabia hailed Morsi's overthrow and pledged billions of dollars to Egypt's military-installed interim government. The Saudi-Egyptian agreement has been ratified by 18 of the Arab League's 22 members.
Egypt had already designated the Muslim Brotherhood as a terrorist group following a suicide bombing that killed 15 people in a police station in December.
Egypt's foreign ministry spokesman Badr Abdelatty said: "We welcome the Saudi decision ... which shows the depth of cooperation and solidarity between the two countries."
"We look forward to see other countries, which signed the 1998 Arab League counter-terrorism treaty, follow the Saudi path and respect their commitments under the treaty," Abdelatty added.
The group condemned the bombing and has denied involvement in any of the violence rocking Egypt since Morsi was ousted by the military in July last year.
The Brotherhood, the largest Islamic movement in the region with a presence in most Arab countries, said it was "surprised" and "pained" by the Saudi decision.
A spokesman for the group said: "This new position the kingdom contrasts sharply with the history of its relations with the Brotherhood.
"History has always shown that the Brotherhood has been a leader in spreading true Islamic thinking ... without extremism, as many of the kingdom's scholars and leaders can testify."