Two people died in clashes with police in northern Tunisia Saturday even as the government reduced the curfew amid fresh signs of returning normality, Tunisia's interior ministry said.

The deaths came as about 300 demonstrators demanded the departure of a local police chief in the northwestern town of Kef, union members said. Protesters set a police station on fire and clashed with police who opened fire killing two demonstrators, aged 19 and 36, they said.

Dozens of members of Tunisia's main trade union also rallied in Tunis demanding a shakeup of its hierarchy.

"Get lost rotten managers!" members of the General Union of Tunisian Workers (UGTT) chanted in front of the union's Tunis headquarters, calling on its secretary general Abdessalem Jrad to step down.

"We ousted (Tunisian president Zine El Abidine) Ben Ali, the time has come to settle accounts with the UGTT's bureaucratic management which flirts with the transitional government and betrays its base," one union member, Habib Ayadi, said.

But in another sign the country was getting back to business, Tunisia's transitional government announced a two-hour shortening of the curfew, which now begins at midnight and ends at 4:00 am (0300 GMT).

Only a few dozen young people still stage peaceful rallies against the former ruling Constitutional Democratic Rally (RCD) party on the city's central Habib Bourguiba artery, scene of massive anti-government protests just three weeks ago.

At one end, a few armoured vehicles belonging to the army are parked in front of the interior ministry. But the machine guns once stationed there are absent.

In another sign of returning normality, Britain lifted its travel warning on Tunisia Friday.

But the interim government remains on the alert, after reporting a mob attack on the interior ministry Monday in what minister Farhat Rajhi described as a "a plot against the state."

Several hundred people also rallied late Friday in front of a police station in the central town of Sidi Bouzid, to protest the deaths of two detainees.

The bodies, both of which showed burn marks, were brought to a hospital, medical staff said. But the circumstances surrounding their deaths remained unclear.

Several police cars were torched during the protest, according to a witness. Two security agents implicated in the burnings were arrested on Saturday, Tunisia's official TAP news agency reported.

Minister Rajhi previously suggested the culprits were supporters of the ousted regime.

It was in Sidi Bouzid that a young man, Mohamed Bouazizi, died after setting himself on fire on December 17, triggering the uprising.

The UGTT was a key player in the protests that ultimately ousted Ben Ali on January 14.

It briefly joined the transitional government of Prime Minister Mohammed Ghannouchi before its members resigned -- although it has offered qualified backing of the since-reshuffled interim government.

The union has been riven by divisions in recent years, with part of its leadership accused of being co-opted by the former regime. A new splinter union, the General Confederation of Tunisian Workers (CGTT) was announced on Tuesday.