A hardline Islamist stabbed two Tunisian policemen on Wednesday in front of parliament, gravely wounding one of them, the interior ministry said.

"A Salafist attacked two policemen with a knife. One was struck on the forehead, and the other stabbed in the neck and is in intensive care," ministry spokesman Yasser Mesbah said.

Outside one of the entrances to parliament, bloodstains were visible at the site of the attack, which was cordoned off by police.

The ministry in a statement said that the assailant was arrested and confessed to having adopted three years ago an extremist line of thought that views members of the security forces as "tyrants".

"Killing them, he believes, is a form of jihad," it said.

An official at the police station where the man was taken after being detained said the attacker was in his 20s and appeared "very aware of what he did".

"He spoke calmly and showed no remorse," the official said, asking to remain anonymous.

"He told us: 'This morning, I prayed and I decided to do something for jihad. I saw the policeman in front of me. To me, he's a 'tyrant'. And I did what I did,'" the official quoted the detained assailant as allegedly saying.

Walid Hkima, a spokesman for the national security forces, told state television the attack happened at around 8am (0700 GMT) and the assailant was quickly arrested.

Since its 2011 revolution, which sparked the Arab Spring, Tunisia has faced a series of jihadist attacks that have claimed the lives of more than 100 soldiers and police.

In 2015, the North African country was the target of several attacks claimed by the Islamic State group that killed 72 people -- 59 of them foreign tourists.

The country has been under a state of emergency since November 2015, after one of those attacks killed 12 presidential guards in the heart of the capital.

In June 2015, 38 foreign tourists, including 30 from Britain, lost their lives in an IS attack on a coastal holiday resort south of Tunis.

In March the same year, another IS attack at the National Bardo Museum in Tunis killed 21 foreign tourists and a policeman.

The Bardo museum is located in the same complex as the parliament.