Dozens of Islamists, some armed with knives, took to the streets of Tunis on Wednesday after deadly clashes overnight, but there was no sign of additional security despite authorities saying there was.
An AFP reporter said a crowd was gathered near the Ennour mosque in the suburb of Manouba, where the interior ministry said a Salafist militant was killed in Tuesday night's clashes.
The government said earlier that police and soldiers had deployed heavily and would use all means to quell any unrest following the clashes sparked by the arrest of a Salafist suspected of assaulting a security official.
But no such forces were visible on the ground, and Islamist militants said they were ready for more confrontations.
"We will not let yesterday's murder pass without any reaction," said one of them.
The interior ministry spokesman warned that, in the event of a new outbreak of violence, security forces would use "all tools permissible by law," including live ammunition if necessary.
Late on Tuesday, militants attacked two national guard posts in Manouba after police arrested a Salafist suspected of assaulting the head of the area's public security brigade, the interior ministry said.
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The attacks were carried out by "a large number of people with radical religious tendencies," ministry spokesman Khaled Tarrouche said.
"The response by the security forces led to the death of an attacker who was hit by a bullet," he said, adding that two policemen were also seriously injured.
Another young militant acknowledged on Wednesday that the violence had been sparked by the arrest of Salafists, but stressed that "this is not a reason to shoot a Tunisian in the head".
The security post at Khalid ibn Walid, where the Salfist was killed, was closed on Wednesday afternoon, although two police cars were parked outside.
Since the Tunisian revolution that ousted president Zine El Abidine Ben Ali in January 2011, radical Islamists have carried out a number of attacks, particularly against security forces and cultural events.
The opposition accuses the government, led by Islamist party Ennahda, of failing to rein in the violence by the Salafists, a hardline branch of Sunni Islam.
But the authorities have vowed to crack down on Islamist violence in the wake of a Salafist-led attack on the US embassy in September in which four assailants were killed.
Ennahda issued a statement on Wednesday appealing for calm and saying the "state has a right to deal with all threats to social peace."