Alexander Downer made the comments after making a telephone call to Chon Jae Hong, North Korea's ambassador to Australia, to protest against the launches.
"We think they probably do intend to launch more missiles in the next day or two," Downer said.
North Korea launched five short-range missiles and a long-range intercontinental missile, known as a Taepodong-2, early on Wednesday.
Australia has backed the UN Security Council decision to hold, at Japan's request, an emergency session on Wednesday to discuss North Korea's tests.
"This is a challenge to international peace and security and it is a matter that should be discussed and considered by the Security Council," Downer told reporters.
John Howard, the prime minister, condemned the missile tests as "extremely provocative" and called on the five nations negotiating with Pyongyang to resolve nuclear tensions on the Korean peninsula to unite in their condemnation.
"I hope that what North Korea has done is condemned as provocative not only by Australia and Japan but also by other countries in the six-power group," Howard told Australian radio, referring to Russia, the US, China and South Korea.
North Korea has suspended six-party talks on its nuclear programme.
"Australia wants North Korea to go back immediately to six-party talks," Howard said.
Downer said that North Korea had demonstrated "a capability, or at least a determination to develop a capability" to develop intercontinental ballistic missiles.
"What really concerns us is the testing of a long-range missile, and that does up the ante in north Asia," Downer said.
Howard said China had more influence than any other country over North Korea and he hoped that it would use this to find a peaceful resolution.
Australia has used its diplomatic ties with Pyongyang to act as an envoy for Washington on the argument over North Korea's nuclear programme.