Rocket and mortar explosions thundered outside Baghdad's heavily protected Green Zone Friday, as Iraq prepared for its first Army Day since U.S. forces invaded the country nine years ago.

Several blasts were heard around midday and were described by Baghdad military spokesman Maj.-Gen. Qassim al-Moussawi as acts of intimidation meant to disrupt the festivities occurring within the Green Zone.

Insurgents were aiming "to prove their presence," al-Moussawi said of the explosions, adding that some of the projectiles landed outside the perimeter of the secured central Baghdad area that houses the U.S. Embassy and several Iraqi government offices.

No casualties were reported immediately following the blasts.

Army officials had said they were on guard for potential attacks in the lead-up to the major military parade, which was attended by Iraqi Prime Minister Nouri al-Maliki and other top Iraqi military brass.

Jan. 6 marks the date that the Iraqi Army was activated 91 years ago, while under British rule.

1st Army Day since U.S. invasion

Friday's ceremony came after a multi-year occupation by U.S. troops, who withdrew from the country last month after leading a 2003 invasion that ultimately ousted dictator Saddam Hussein from power.

The explosions on Friday came the day after the country's deadliest sectarian violence in more than a year left scores of people dead, officials said.

The Iraqi Army was activated on Jan. 6, 1921, while under British rule. (Hadi Mizban/Associated Press)

A wave of bombs on Thursday struck two Shia neighbourhoods, killing at least 78 people and renewing fears of another cycle of sectarian fighting. It also marked the second large-scale attack by militants since the U.S. pullout.

Elsewhere in Bahgdad on Friday, at least three roadside bombs in different districts of the capital exploded in the morning, killing two Shia pilgrims and wounding 17 other people, according to police and hospital officials.

The attacks occurred in the run-up to Arbaeen, a holy day that marks the end of 40 days of mourning following the anniversary of the death of Imam Hussein, a revered Shiite figure. During this time, Shiite pilgrims — many on foot — make their way across Iraq to Karbala, south of Baghdad.

The violence in Iraq comes as the country's main factions are mired in a crisis pitting politicians from the Shiite majority now in power against the Sunni minority, which dominated government under the dictatorship of Hussein .

With files from The Associated Press