(Adds comments from interior minister)

ALGIERS, May 16 (Reuters) - Algeria's government condemned a bomb attack on Wednesday as an "act of sabotage" aimed at disrupting Thursday's legislative elections and urged Algerians to turn out in large numbers.

The small bomb exploded near a police roadblock in eastern Algeria, killing a policeman and wounding two other people, residents and the official APS news agency said.

The device, believed to have been rigged inside a package, went off in the poor Dakssi neighbourhood of the city of Constantine 320 km (200 miles) east of Algiers, residents said.

They said the bomb was believed to have been placed by Islamist rebels seeking to set up Islamic rule in the large oil- and gas-exporting north African country.

"We have been expecting this kind of act. It is an act of sabotage, an act against the democratic system in Algeria," Interior Minister Noureddine Yazid Zerhouni said in remarks carried by APS.

"The best way of responding to this kind of attack is strong participation in the legislative elections," he said.

Algerians go to the polls on Thursday to choose the 389 members of the lower house of parliament, the third time they have done so since an Islamist revolt erupted after the cancellation of a general election in January, 1992.

Supporters of a now-outlawed Muslim fundamentalist party that was poised to win those elections subsequently launched an armed rebellion against the state.

Up to 200,000 people have been killed in political bloodshed since then, and while the violence has dropped sharply in recent years a recent spate of bombings claimed by armed Islamist groups has threatened Algeria's attempts to rebuild.

President Abdelaziz Bouteflika offered an amnesty for Islamist rebels last year as part of a peace and reconciliation policy aimed at ending almost 15 years of political violence.

More than 2,000 rebels were freed from jail and dozens of fighters surrendered under the amnesty, which lasted from late February to late August 2006.

But Algeria's main rebel group, the al Qaeda Organisation in the Islamic Maghreb, previously known as the Salafist Group for Preaching and Combat, or GSPC, has rejected the amnesty offer and vowed to fight on until purist Islamic rule is established.

The group claimed responsibility for triple suicide bombings that killed 33 people in Algiers on April 11, and vowed to carry out more attacks.

Zerhouni sought on Wednesday to reassure voters the security situation was under control. "Security measures have been taken to ensure the poll takes place in good conditions," he said.

Zerhouni vowed in Wednesday's edition of government-backed newspaper El Moudjahid to fight against Islamist rebels. "The fight against terrorists will go on without respite," he said.

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