The latest deaths raised to 49 the tally of jihadists killed since Monday's assault in Ben Guerdane, near Libya's border, on an army barracks and police and National Guard posts.
One of the jihadists was killed in Zokra district after he shot at an army and police patrol, the interior and defence ministries said in a joint statement yesterday.
The two others were killed in Hassi al-Nour district, where another man was also detained and four Kalashnikov rifles were seized, it said.
Thirteen members of the security forces and seven civilians were killed in Monday's attacks, according to official figures.
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There has been no claim of responsibility for the attacks, but the authorities have blamed them on the Islamic State jihadist group present in neighbouring Libya.
IS has taken advantage of a power vacuum in Libya since the NATO-backed overthrow of longtime dictator Moamer Kadhafi in 2011 to set up bases in several areas, including near Sabratha close to the Tunisian border.
A nighttime curfew and tight security remain in place in Ben Guerdane, a city of around 60,000 inhabitants.
Tunisia has built a 200-kilometre barrier that stretches about half the length of its border in an attempt to stop militant incursions from Libya.
Last year IS -- which has seized large parts of Syria and Iraq and is also active in Egypt -- claimed three attacks in Tunisia, killing dozens of foreign tourists and presidential guards.