The suspect in Norway's twin attacks that killed at least 93 people and wounded nearly 100 more claims he acted alone, police said Sunday as a raid on an Oslo flat failed to find any link to the attacks.

Prime Minister Jens Stoltenberg and Norway's King Harald V and Queen Sonja led the nation in mourning at an emotional memorial mass in Oslo Cathedral for the victims of Friday's twin bomb and gun attack.

The United States said Sunday it has invited a top North Korean envoy to New York for "exploratory talks" on the possible resumption of the six-party negotiations on denuclearization.

Secretary of State Hillary Clinton said the North's vice foreign minister and former nuclear negotiator, Kim Kye-Gwan, would visit the U.S. at the "end of next week".

The Norwegian royal couple, Prime Minister Jens Stoltenberg and other ministers attended a somber mass at Oslo cathedral on Sunday in memory of the 92 people killed in Friday's twin attacks.

Hundreds of ordinary citizens gathered outside the cathedral where a shrine has been set up amid a sea of flowers laid in tribute to those killed in the bombing in Oslo and a mass shooting on a nearby island.

Venezuelan President Hugo Chavez returned to his country Saturday after undergoing chemotherapy treatment for his cancer in Cuba, local television reported.

The 56-year-old leader underwent an operation in Cuba a month ago for a cancerous tumor in his pelvic area.

A gunman opened fire at a skating rink in the town of Grand Prairie, Texas, Saturday, killing at least five people and injuring four others before committing suicide, police said.

The shooting followed a fight that broke out at a birthday party at the roller skating rink, said a police official who spoke on condition of anonymity.

A Chinese high-speed train derailed Saturday when it was hit by another express, state media said, throwing two carriages off a viaduct and killing at least 32 people.

The derailed train had been crippled by a lightning strike and was stationary when the second one ploughed into it, the reports said. The accident is likely to raise new questions about the safety of a rapid rail expansion.

The Norwegian suspect in the double attacks that left at least 92 dead described himself as a fundamentalist Christian, said police, as evidence emerged that he had flirted with the political far-right.

The 32-year-old, previously unknown to police, was arrested Friday after a bomb blast in central Oslo killed seven people and a shooting rampage at a youth camp near the capital left at least 85 dead and scores wounded.

Leaders of Sudan's main opposition group, whose men are fighting government troops in South Kordofan, on Saturday rejected calls to disarm and said they would negotiate only via an outside third party.

The northern branch of the Sudan People's Liberation Movement, the ruling party of South Sudan, in a statement also accused the government of seeking to destroy north-south relations just two weeks after formal southern independence.

A burqa and niqab ban came into force in Belgium on Saturday with the threat of fines and jail time, but the law faced an immediate court challenge from two women who wear the full Islamic veil.

Belgium joined France as the second European Union nation to enforce such a ban.

Norwegian police arrested a young man carrying a knife Saturday at a hotel where Prime Minister Jens Stoltenberg was visiting survivors of a shooting rampage that left 85 dead, broadcaster NRK said.

The suspect said he was a member of the Labor party's youth wing and that he had a knife in his pocket "because he did not feel safe," an NRK reporter said.