Syria's health minister says 50 people have been killed in two strong explosions that ripped through the Syrian capital.

That makes Thursday morning's bombings the deadliest attack on the capital since the country's uprising began 14 months ago. There was no immediate claim of responsibility.

The explosions heavily damaged a military intelligence building and left blood and human remains in the streets.

The blasts happened at about 7:50 a.m., when employees are usually arriving at work.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

DAMASCUS, Syria (AP) _ Two strong explosions ripped through the Syrian capital Thursday, killing more than 40 people and leaving scenes of carnage in the streets in an assault against a center of government power, officials said.

Syria's state-run TV said 170 people were wounded in what one official said may have been the most powerful of a series of blasts that have hit the capital this year.

There was no claim of responsibility for Thursday's attack on a military intelligence headquarters. But an al-Qaida-inspired group has claimed responsibility for several large explosions targeting mostly security facilities since December, raising fears that extremist groups are entering Syria's conflict and exploiting the chaos.

The regime has used the bombings to support its claims that terrorists rather than a popular uprising are behind Syria's violence. The relentless violence by both sides of the conflict has brought a U.N.-brokered ceasefire plan to the brink of collapse.

Thursday's explosions, which ripped the facade off the intelligence building, went off at about 7:50 a.m. when employees are usually arriving at work. The building is part of a broader military compound for a feared section of the intelligence services known as the Palestine Branch.

An Associated Press reporter at the scene said paramedics wearing rubber gloves were collecting human remains from the pavement after the explosions. Heavily damaged cars and pickup trucks stood smoldering in the area. The outer wall of the headquarters collapsed and some walls crumbled, although the basic structure inside appeared intact.

The Syrian government blamed "terrorists" and said dozens were killed or wounded, most of them civilians.

Maj. Gen. Robert Mood, the Norwegian head of the U.N.'s cease-fire monitors in the country, toured the site and said the Syrian people do not deserve this "terrible violence."

"It is not going to solve any problems," he said, when asked what his message was to those who are carrying out such attacks. "It is only going to create more suffering for women and children."

Central Damascus is tightly under the control of forces loyal to President Bashar Assad but has been struck by several bomb attacks, often targeting security installations or convoys. The latest major explosion in the capital occurred on April 27 when a suicide bomber detonated an explosives belt near members of the security forces, killing at least nine people and wounding 26.

Foreign Ministry spokesman Jihad Makdissi posted a message on his Facebook page urging people to go to hospitals to donate blood, saying that Thursday's blast "might be the strongest" of a wave of explosions that have hit Damascus since late December.

The explosions left two craters at the gate of the military compound, one of them 3 meters (10 feet) deep and 6 meters (20 feet) wide. Residents said the two explosions quickly followed each other: first a smaller blast, then a massive one.

"The house shook like it was an earthquake," said housewife Maha Hijazi, who appeared shaken as she stood outside her house across the street from the targeted compound.

Thursday's bombings were among the deadliest since such spectacular attacks started in December 2011, with a double suicide bombing of a Damascus security building that killed at least 44 people. Fresh attacks have followed in other cities, including Idlib in the north and Aleppo, Syria's largest city and long considered an Assad stronghold.

Most of the attacks target state security offices and occur early morning.

The government blames the bombings on the terrorists it says are behind the anti-Assad uprising. Opposition leaders and activists routinely blame the regime for orchestrating the attacks, saying they help it demonize the opposition and maintain support among those who fear greater instability.

A shadowy group called the Al-Nusra Front has claimed responsibility for some of the attacks in statements posted on military websites. Little is known about the group, though Western intelligence officials say it could be a front for al-Qaida's Iraq branch.

International diplomacy has failed to stop the bloodshed, and the U.N. has ruled out military intervention of the type that helped bring down Libya's Moammar Gadhafi, in part out of fear that it could exacerbate the violence.

Special envoy Kofi Annan brokered a peace plan last month, but the initiative has been troubled from the start, with government troops shelling opposition areas and rebels attacking military convoys and checkpoints after the cease-fire was supposed to begin on April 12. Many civilians have grown critical of the plan, saying it does not protect them from regime forces.

Although the daily death toll has dropped in recent days, Annan said Tuesday that the level of violence is unacceptable and that the plan's failure could lead to civil war.

A team of 70 U.N. military observers now in Syria should grow to more than 100 in the coming days. A full team of 300 is expected by the end of the month to oversee a cease-fire intended to allow for talks on a political solution to the conflict.

On Wednesday, a roadside bomb hit a Syrian military truck in a southern province just seconds after the U.N.'s Maj. Gen. Mood was driving by in a convoy, demonstrating the fragility of the international plan to end the country's bloodshed.

Syria's conflict started in March 2011 with mass protests calling for political reform. The government swiftly cracked down, dispatching tanks, troops, snipers and pro-government thugs to quash dissent, and many members of the opposition took up arms to defend themselves and attack government troops. Many soldiers also switched sides.

The U.N said weeks ago that more than 9,000 people had been killed. Hundreds more have died since.

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AP writer Ben Hubbard contributed to this report from Beirut.