The five were among a group of 34 who were detained for questioning at the Habur crossing point after entering Turkey on Monday in a show of support for a peaceful solution of the Kurdish conflict. The other 29 were released.

Among those who remained in custody were three militants from the outlawed Kurdistan Workers' Party (PKK), which has led a bloody rebellion against Ankara in the Kurdish-majority southeast since 1984.

A prosecutor demanded the five be formally charged with unspecified crimes committed in the past and a judge was to make a decision later Tuesday, the sources said.

The PKK militants' crossing to Turkey amounts to surrendering to the Turkish authorities, who consider the group a terrorist organisation.

Heeding a proposal from its jailed leader Abdullah Ocalan, the PKK announced last week it would send "peace groups" from Iraq, where the rebels have rear bases, and Europe, in a gesture of support for a government initiative to expand Kurdish freedoms.

Since August, the government has been trying to build public support for fresh reforms to grant Kurds greater rights.

Ankara however rejects dialogue with the PKK and has vowed to pursue military action against it.

Monday's 'peace group' included 26 Turkish Kurds from the UN-run Makhmour refugee camp in northern Iraq which houses some 12,000 people who fled Turkey in the 1990s at the peak of the conflict.

Two groups of PKK militants came to Turkey in 1999 on a similar peace mission, but they were arrested and then jailed for belonging to the PKK.