British Prime Minister David Cameron outlined plans on Friday to seize passports from British jihadists and stop them returning from fighting overseas, while proposing landing bans on airlines that fail to comply with London's no-fly lists.

Some 500 radicalized Britons are estimated to be fighting in Iraq and Syria, both of which are facing a major offensive from the Islamic State militant group.

"We will shortly be introducing our own new Counter-Terrorism Bill in the UK," Cameron said in a speech to Australia's Parliament before traveling to the G20 leaders' summit in Brisbane, adding that there was "no opt-out from dealing with this".