World News Update, what you need to know

Governments across the world have begun investigating possible financial wrongdoing by the rich and powerful after a leak of four decades of documents from a Panamanian law firm that specialised in setting up offshore companies.

WELLINGTON, April 5 AAP - Former New Zealand prime minister Helen Clark is joining the race for the top job at the United Nations.

WASHINGTON - Recent satellite images have shown "suspicious" activity at North Korea's main nuclear site at Yongbyon, suggesting reprocessing is under way to produce more plutonium for atomic bombs.

MILWAUKEE - Republican presidential frontrunner Donald Trump is trying to put a difficult week behind him and rally supporters ahead of a crucial nominating contest in Wisconsin, where he's in the unfamiliar position of underdog.

WASHINGTON, April 4 Reuters - US President Barack Obama and NATO Secretary-General Jens Stoltenberg say NATO can help Libya counter Islamic State militants as well as train and assist troops in Iraq, Jordan and elsewhere to fight the insurgent group.

BAGHDAD - Militants have unleashed a wave of suicide attacks across Iraq, killing at least 29 people and wounding dozens, officials say.

LONDON - Estate agents dealing with the sale of an entire English village say they have been inundated with inquiries despite the STG20 million ($A37.11 million) price tag.