Iraq has blamed Iran for chaos on the border as thousands of foreign pilgrims stormed the fences and wounded border guards to illegally enter the country for a major Shiite ritual -- Arba'een.

A stampede took place at the Zurbatiyah border crossing point with Iran during the last two days, the Iraqi Interior Ministry said in a statement, Xinhua reported.

Apparently thousands of pilgrims did not obtain visas to enter the country, the ministry added, holding Iranian authorities responsible for the chaos.

"We hold the Iranian side responsible for (the incident) because they did not abide by their duties and obligations in a manner that would prevent the breakdown of the situation on the border crossing point," it said.

It further said that the uncontrolled flow of crowd was deliberate to exercise pressure on officials of the crossing point so it will be illegally opened under the pretext that the Iranian side could not control the entrants from Iran.

Previously, an agreement was reached between the two countries for the Iranian side to prevent individuals who did not get visas from approaching the Iraqi side of the border crossing point, according to the statement.

Millions of Shiite pilgrims from the Muslim world travel to Iraq heading to the holy Shiite city of Karbala, south of Baghdad, to observe Arba'een rituals for Imam Hussein, ahead of it on Thursday.

Arba'een is the 40th day after the death of Imam Hussein, Prophet Muhammad's grandson and the third holy figure for the Shiite Muslim sect. He was killed in the battle of Karbala in 680 AD and is buried in Iraq.

IANS adds from New Delhi: Millions are willing to risk their lives in spite of terror threats to reach Karbala to mark "Chehlum".The pilgrimage is seen as a response of faith to Isis which has threatened pilgrims with terror attacks.

The Arba'een is the world's largest gathering of Shias and some say the number of pilgrims far exceeds that of visitors to Mecca for the Haj which draws around two million people. Last year, Arba'een drew 20 million mourners.

The pilgrimage was banned under Iraqi dicator Saddam Hussein but was reintroduced in 2003 after his ouster.