Madrid  - The Spanish government is preparing to toughen the country's anti-terrorism laws as the hunt for former ETA prisoner Ignacio de Juana Chaos in Ireland continued Wednesday.

The daily El Pais reported on Wednesday that new government measures will mainly target members of the militant Basque separatist group ETA, and are intended to bring the penalties for terrorism offences as close as possible to life imprisonment, which is deemed incompatible with the Spanish constitution.

Prime Minister Jose Luis Rodriguez Zapatero's government intends to establish the possibility of placing former terrorists under permanent surveillance after they have served their prison sentences, the paper said.

The possible measures will include electronic bracelets to allow police to locate former terrorist convicts any time, prohibitions on ex-convicts living near victims and orders to report regularly in a place determined by a judge.

The measures can be applied for up to 20 years.

The government is trying to prevent a repeat of cases such as that of Ignacio de Juana Chaos, a notorious former ETA prisoner.

De Juana was released in August after serving 21 years of a sentence of more than 3,000 years for participating in 11 attacks that killed 25 people, and for writing articles favourable to terrorism.

De Juana is now suspected of having committed another offence of praising terrorism, for which reason an international arrest warrant was issued for him after he failed to show up in court for questioning on Tuesday.

De Juana is believed to be moving between the Republic of Ireland and Northern Ireland.

Irish police Tuesday detained four people at a Dublin address which de Juana had given as his contact address when applying for a new passport, the Spanish daily El Mundo reported.

The address was that of James Monaghan, a former member of the Irish Republican Army (IRA). The detainees were members of his family, according to the daily.

Information given by Irish police indicated that the arrests were made in connection with the planting of an explosive device outside the Irish headquarters of the oil-firm Shell last year, and were not immediately linked with de Juana. Irish police declined to comment on the search for de Juana. (dpa)