Deadline (1982)

"It's the most lethal deadline in history and if it's not met, three and a half million people will die!"

A journalist sets out to report on a minor earthquake in the Australian outback, and finds that the tremor was a result of a small nuclear explosion - part of an extortion threat that has the government fearing nuclear blackmail. With the help of local reporters, and despite the harassment of the security agencies, he sets out to avert the crisis.