Fighting has spread across Damascus, as the Syrian capital has become enmeshed in the kind of fighting that has so far been reserved for other cities in the 16-month-old uprising against President Bashar al-Assad.

Opposition forces struck their heaviest blow yet, detonating a bomb attack in the heart of Assad's Damascus stronghold that killed several of the government's highest officials, including the defense minister and the deputy defense minister, who is Assad's brother-in-law. Wounded in the attack were the interior minister and the head of the National Security Department.

Assad appeared on state-run television to administer the swearing-in of a new defense minister but only after a full day had passed since the bombing. In between, government helicopters and artillery had fired on rebel positions in Damascus, extending to five the number of days of intense fighting in the capital. Reports came in of an opposition attack on police headquarters.

Refugees in the thousands streamed across the border into Lebanon, as the opposition claimed control of several key points along the borders with Turkey in the north and Iraq in the southeast, including along the Baghdad-Damascus Highway at the major city of Abu Kamal, one of the most important trade routes in the Middle East. Syria's other neighbors are Israel, Jordan, and Lebanon.

Western powers again tried to secure a resolution against Syria in the United Nations Security Council. As before, both China and Russia vetoed the measure. Both countries have repeatedly refused to place the blame solely on Syria. Russia still sells weapons to the Syrian government.

Part of the resolution was an extension of a U.N. monitoring mission, which has seen 300 "peace-keeping" monitors largely sidelined because of the continued intensity of the violence. Neither the government nor the opposition has paid much attention to a six-point peace plan put forward several weeks ago by U.N. special envoy Kofi Annan.

Assad's government has repeatedly blamed the resistance on foreign influences. Opposition leaders have repeatedly blamed the government for refusing to stop the shelling, in Damascus and Homs and Aleppo and other In the latest statement, the government warned Syrian citizens to be on the lookout for opposition fighters dressed as government soldiers. Both sides have blamed each other for attacks on unarmed civilians.

According to human rights groups, more than 17,000 people have died since March 2011. Most of those dead have been civilians. The government has reported that more than 4,000 security officers have died in the conflict.