Egypt's interim leader Adli Mansour has issued a decree outlining the election timetable in a swift move to pull the country out of the ongoing crisis.

The decision by Mansour, who was appointed by the powerful army after ousting Mohamed Morsi, comes after a shooting incident in Cairo killing dozens.

The decree requires Egypt to hold parliamentary elections within six months quickly followed by presidential polls.

According to the constitutional declaration, Mansour will also appoint a committee to oversee amendments to the Islamist-drafted constitution which was passed during Morsi's administration. The panel will be formed within two weeks and it will have one month to make the statute changes.

A referendum on the amended constitution will be held in four months' time which will pave the way for the parliamentary elections possibly by early 2014.

The decree also appears to contain flaws found in the earlier transitional plan in 2011 which later led to the Muslim Brotherhood taking power.

The constitution framed by the Islamist assembly was a key point of disagreement between Morsi and his liberal opponents when he was in power.

Morsi's supporters and Brotherhood leaders have not yet publicly commented on the latest declaration.

It comes into force with immediate effect following the bloody gunfire outside Cairo's Republican Guards barracks in which 51 people were killed and 435 injured.

The military said its men opened fire in retaliation against the armed provocation of Brotherhood supporters.

Although it is still unclear what led to the carnage, both sides are pointing fingers at each other.

The interim administration has also expressed "deep regret" over the shooting incident and vowed to probe the killings.

The US has condemned the shooting and urged "maximum restraint".

Egypt's top Muslim cleric, Sheikh Ahmed el-Tayeb, has warned of Egypt plunging into a civil war and announced he would go into seclusion until the unrest ends.

The Brotherhood has called for more protests later in the day defying the army and the interim government. The situation continues to be volatile as it is feared that violence could break out during the rallies.

Top leaders are likely to focus on avoiding further bloodshed and choosing an interim prime minister to press ahead with the proposed elections.