Tunisian security forces were on Thursday hunting two armed jihadist groups near the Algerian border, the interior ministry said, as the authorities battle an Islamist threat that has grown increasingly dangerous.

"There are two groups, one of about 15 to 20 people in Mount Chaambi... Another group is in the Kef region near the Algerian border," ministry spokesman Mohamed Ali Aroui told AFP.

"There are no (direct) clashes taking place. We are combing the region with guns," he added.

A security source said on Wednesday that troops clashed with around 50 armed Algerian and Tunisian jihadists in the Chaambi region, which is completely surrounded by the army.

Tunisian forces have been hunting for the group holed up in the mountainous western region since Monday. The authorities have described them only as "terrorists."

In the operation to flush them out, around 15 soldiers and members of the national guard have already been wounded, some seriously, by homemade landmines laid by the gunmen.

The defence ministry said the army had the situation along the border "under control" but was unable to give more details about those targeted in the operation, or about the second group in the Kef region, around 100 kilometres (60 miles) to the north.

"We can't give more information for security reasons," Colonel Mokhtar Ben Naceur told Tunisian radio, adding that it was "a difficult region and the hunt continues."

Earlier he admitted he had "no idea" about the number of people the security forces were pursuing, or about the second group in the Kef region, and said no one had yet been arrested.

Asked about cooperation with Algeria, the colonel said that Tunisia's neighbour was helping but only at the level of intelligence-sharing.

"There is no joint action on the ground," he said.

On Wednesday the defence ministry said no direct fighting had taken place and that troops were demining the mountain with the help of "small arms and mortars." The area covers around 100 square kilometres, 60 of which are forested.

Since the mass uprising that toppled Zine El Abidine Ben Ali in January 2011, radical Islamists suppressed by the former dictator have become increasingly assertive and been blamed for a wave of deadly attacks across the country.

Members of the armed forces involved in the search have told media that the Mount Chaambi group is well-armed and organised, with some saying veteran Islamist militants who fought in northern Mali are among them.

The current government, led by the moderate Islamist party Ennahda, has fully recognised the jihadist threat facing Tunisia, warning that groups linked to Al-Qaeda in the Islamic Maghreb were infiltrating its borders.

But it has been strongly criticised by the opposition, who accuse Ennahda of failing to rein in Islamist militants, or facing up to the threat they pose too late, despite the security problems they have caused since the revolution.

The security forces are also growing increasingly frustrated, criticising their lack of equipment, with up to 400 demonstrating outside the national assembly on Thursday to demand better resources.

"Citizens, wake up! Terrorism has invaded our country," they chanted.

The group being hunted in the Chaambi region was blamed for an attack on a border post in December that killed a member of the national guard, and the security forces have been searching for the jihadists ever since.

To date 37 people have been caught and jailed, the interior ministry spokesman said, without indicating whether the number included 16 jihadists linked to an alleged Al-Qaeda cell who were arrested after the December attack.