The United States said Thursday the most senior leader of the extremist Haqqani group yet "taken off the battlefield" had been killed in a lawless tribal area of Pakistan.

"It's been confirmed that Janbaz Zadran, aka Jamil, was killed earlier today in North Waziristan, Pakistan," said a senior US official, revealing the death of the latest target of the secret U.S. anti-terror war.

Norwegian extremist Anders Behring Breivik, who has confessed to twin attacks in July that killed 77 people, will be allowed out of solitary confinement but will still be subjected to heavy restrictions, police said Thursday.

"We will not extend the solitary confinement beyond October 17," police prosecutor Christian Hatlo told reporters.

Judges trying ex-Bosnian Serb army chief Ratko Mladic turned down Thursday a prosecution bid to hold two separate trials, the first focusing on the Srebrenica massacre.

"The Trial Chamber today denied the Prosecution's request to sever the indictment against Ratko Mladic," a statement said, upholding a challenge filed by Mladic's lawyer Branko Lukic against the prosecution bid.

A powerful explosion likely triggered by a gas leak ripped through a restaurant in downtown Rio de Janeiro early Thursday, leaving three people dead and 17 injured, the Brazilian city's mayor said.

Three of those hurt were in serious condition, Mayor Eduardo Paes told reporters at the scene of the explosion, which occurred around 7:30 am (1030 GMT).

Two suspicious packages delivered to Swedish government buildings triggered bomb scares Thursday, police said, amid reports one may have been a gift from Uruguay's visiting president.

Police were alerted to a suspicious letter or package at the Rosenbad building, which houses Prime Minister Fredrik Reinfeldt's offices, late Thursday morning and decided to evacuate parts of the building and cordon off the surrounding block, Stockholm police spokesman Ulf Lindgren told AFP.

Somali Islamist Shebab rebels on Thursday kidnapped two female Spanish aid workers from Kenya's Dadaab refugee camp, a regional police official said.

"Two aid workers of Spanish nationality have been kidnapped by the Shebab, they are working for MSF (Medecins Sans Frontieres)," Leo Nyongesa, regional police chief, told AFP.

British Foreign Secretary William Hague said Thursday that an alleged Iranian-backed plot to kill the Saudi envoy to the United States is a "major escalation in Iran's sponsorship of terrorism."

Hague said London was in "close touch" with U.S. authorities and would work to agree an international response along with the United States, European Union and Saudi Arabia to the U.S. charges, which Tehran denies.

At least 43 people were killed Thursday when a bus veered off a mountain road in eastern Nepal and plunged into a river, officials said.

The bus swerved off an unfinished stretch of road and plummeted 300 meters into the fast-flowing water below, said Lokendra Shrestha, a police officer in Sindhuli district, around 80 kilometers east of Kathmandu.

An Amtrak train crashed into another train unloading passengers in an Oakland station late Wednesday, injuring 16 people, authorities said.

The train was traveling an estimated 15 to 20 miles per hour when it struck the stationary Amtrak passenger train about 10 p.m., said Oakland Fire Department battalion chief Emon Usher.

Two U.S. drone strikes on Thursday killed at least 10 militants in Pakistan's northwestern tribal belt, including a commander in the al-Qaida-linked Haqqani network, local officials said.

The first strike targeted the Haqqani commander in North Waziristan, killing him and three guards, while a second attack hit the Birmal area in the neighboring district of South Waziristan close to the Afghan border.