British media on Tuesday voiced skepticism over "vague" plans announced by Prime Minister David Cameron to counter the threat of jihadist fighters traveling to Iraq and Syria.

Cameron said that among the measures envisaged was a plan to give border police powers to seize passports from departing would-be jihadists and restricting the movement of suspects.

But he failed to give details or a timetable for implementation and said a proposal to block suspected fighters from returning to Britain was being looked at.

The proposal is a controversial one in international law as it would be illegal to make British nationals "stateless".

"He is doing all he can to sound tough without having the detail in place to back up the rhetoric," wrote Rachel Sylvester, a political commentator for the Times.

She cited the former head of public prosecutions Ken Macdonald as saying that officials were in "la-la land" if they thought the idea of blocking jihadists would be accepted by the international community.

Britain estimates more than 500 of its citizens have joined Islamist radicals in Iraq and Syria.

The Guardian newspaper said Cameron's proposals still left a "gaping hole" in tackling the problem.

The Daily Mirror tabloid called the measures "vague" and said there had been little support for them from the Liberal Democrats, the junior coalition partner in Cameron's government.

The Daily Mail said the measures were "chaotic".

The Financial Times said the proposals could rile Turkey, a major transit point into Syria, which could be forced to host British jihadist fighters not allowed back to Britain.