The UN envoy to Iraq said Thursday there was a "window of opportunity" for Baghdad to resolve a pre-election crisis sparked by the resignation en masse of its election commission.

Iraqi Prime Minister Nuri al-Maliki warned Wednesday that April 30 legislative elections may be delayed given Tuesday's resignations, and with violence at its worst in six years.

But in New York, Nickolay Mladenov, the UN special representative to Iraq, gave a slightly more upbeat assessment.

He said the resignations of the Independent High Electoral Commission (IHEC) had not yet been formally endorsed by the speaker of Iraq's parliament.

"This gives a window of opportunity for the Iraqi parliament to address the concerns that the commissioners have," he said.

IHEC's board has been frustrated with what they say is a vague provision in Iraq's electoral law that requires parliamentary hopefuls to be "of good reputation."

Mladenov described the commission as "technically well prepared," and defended the "integrity" of its commissioners.

"This will be a very contested election but we look forward to a good process that will ensure all Iraqis have the ability to vote freely and fairly," Mladenov told reporters.

The UN envoy said escalating violence in Iraq, which has surged to levels not seen since 2008, required a "holistic" solution.

"You cannot resolve the problem of violence or terrorism simply by security measures. Security measures are very important but you need a holistic approach," he said.

Economic measures, human rights and the inclusion of all communities in decision-making was required, Mladenov said.