Protesters started to gather in Cairo on Tuesday for rival rallies for and against a divisive constitutional referendum proposed by Egypt’s president, Mohammad Mursi.

Protesters started to gather in Cairo on Tuesday for rival rallies for and against a divisive constitutional referendum proposed by Egypt's president, Mohammad Mursi.

The competing demonstrations carried the risk of further violence, after street clashes last week between opposition and Islamist supporters left seven people dead and hundreds hurt. However, no violent incidents were seen.

Around a couple of hundred opposition protesters tried to break through metal crowd barriers set up outside presidential palace.

But hundreds of soldiers, and some riot police, kept the defensive line. Behind them were stationed tanks and armored personnel carriers deployed since last week.

On the other side, a counter-demonstration in favor of the referendum also took place a mere two kilometers (one mile) away at the behest of the pro-Mursi Coalition of Islamist Forces.

The opposition, made up of secular, leftwing and liberal groups, has vowed to scupper the referendum and the draft constitution, which was approved by an Islamist-leaning panel.

The UN human rights chief and international rights groups have criticized the draft charter and the way it was rushed through.

Mursi's supporters, though, argue that it is now up to Egypt's voters to decide it in the referendum.

On Monday, after a meeting with Mursi, Egypt's defense minister and commander of the armed forces, General Abel-Fattah al-Sisi, called on army officers to exercise the "highest levels of self-restraint".

He said the armed forces were determined to "carry out their role in protecting the nation and its stability regardless of pressures and challenges".