Howard declined to give details about the information at a press conference in the capital Canberra on Wednesday and said the national terror alert level would not be raised.
"We have seen material; it is a cause of concern; we have been given advice that if this amendment is enacted as soon as possible, the capacity of the authorities to respond will be strengthened," the prime minister said.
His government has quickly pushed an amendment through the lower house of parliament to beef up proposed anti-terror laws.
Critics have condemned the new measures as a threat to civil liberties.
Prime Minister Howard said the legal amendment, to be approved by the Senate on Thursday, would help the government deal with the new threat.
"The government is satisfied on the advice provided to it that the immediate passage of this bill would strengthen the capacity of law enforcement agencies to effectively respond to this threat," he said.
Howard said the amendment meant that when prosecuting someone for planning a terrorist act, authorities would not have to identify a specific terrorist act.
It will also allow groups to be banned based on intelligence that it is preparing an unspecified terrorist act rather outlining details of a specific terror plot.
"They now want to ban organisations that aren't necessarily terrorist groups but might advocate terrorism"
Intelligence expert Aldo Borgu said the government may be planning to ban Islamic group Hizb ut-Tahrir.
"They now want to ban organisations that aren't necessarily terrorist groups but might advocate terrorism," said Borgu, an analyst from the Canberra-based Australian Strategic Policy Institute.
Howard has been a loyal ally in the US-led "war on terror" and contributed troops to the wars in Iraq and Afghanistan. Australian intelligence on Tuesday issued a report raising the spectre of home-grown terrorism.
"The government is acting against the background of the assessment of intelligence agencies that a terrorist attack in Australia is feasible and could well occur," he said, referring to the report.
The government drafted the new
laws after the London bombings
The amendment is part of controversial new anti-terror laws that the government drafted after the London transport bombings by British-born Muslims in July that killed more than 50 people.
The package of new legislation will be introduced in parliament soon and the government hopes to get it passed by Christmas, Howard said.
The new laws, under which suspects can be detained without charge for up to two weeks, placed under house arrest and fitted with tracking devices, have been widely criticised as infringing on civil liberties.
The Australian spy agency ASIO said in its report to parliament on Tuesday that some Australian Muslims believed there was "a battle between Muslims and infidels".
The Australian embassy in
Jakarta was attacked in 2004
They felt "a sense of hostility and isolation towards the broader Australian society", with some viewing the US-led invasion of Iraq as an attack on all Muslims, the report said.
The philosophy "extends to support for violence against the 'un-Islamic' governments, against perceived Western invasion of countries and against countries they believe are attacking Islam and oppressing Muslims".
"This support can extend to funding and terrorist training activity as well as participation in overseas conflicts."
The report said that "some of the more extreme individuals ASIO has identified and investigated are Australian-born. Some have participated in terrorist training overseas while others have never travelled abroad".
Australia has not been attacked on its own turf but Australian interests have been targeted elsewhere.
A bomber hit the Australian embassy in Jakarta last year, and dozens of Australians were killed in attacks on nightclubs on the Indonesian resort island of Bali in 2002.