(L-R) Former Syrian defense minister Gen. Hassan Ali Turkmani, Defense Minister Dawoud Rajhah and Asef Shawkat, the brother-in-law of Syrian President Bashar Al-Assad are seen in this combination photo. — Reuters BEIRUT — In the harshest blow to Syria's ruling family dynasty and the rebels' boldest attack in the country's civil war, a bomb in Damascus Wednesday killed three of the country's top security officials including a brother-in-law of President Bashar Al-Assad. The blast, an audacious strike that has crippled the government, killed Defense Minister Dawoud Rajhah, Deputy Defense Minister Gen. Asef Shawkat and Gen. Hassan Ali Turkmani, a former defense minister and senior military official. Intelligence chief Hisham Bekhtyar and Interior Minister Mohammad Ibrahim Al-Shaar were wounded but were “stable”. Syrian state-run TV said the blast came during a meeting of Cabinet ministers and senior security officials in Damascus, which has seen four straight days of clashes between rebels and government troops. The attack prompted the White House to say Assad was “losing control” of his country. The high-level assassinations could signal a turning point in the civil war as the violence becomes increasingly chaotic. The Free Syrian Army, the rebel umbrella group, took responsibility for the blast. The killing of Shawkat, who had reportedly been targeted in other plots, hits directly at the Assad family, which has ruled Syria for more than 40 years. He reportedly was married to Assad's sister, Bushra, and was considered a key figure in the inner circle of the government.Syria's rebel commander, Riad Al-Asaad, said his forces carried out the attack. Although state-run TV said it was a suicide blast, Al-Asaad said his rebel forces planted a bomb in the room and detonated it. All those involved in carrying out the attack are safe, he said. “God willing, this is the beginning of the end of the regime,” Al-Asaad said from his base in neighboring Turkey. “Hopefully Bashar will be next,” he added. It was not immediately clear where Assad was; he gave no immediate statements on the attacks, although in the hours after the assassination, Syria's state-run TV said a decree from Assad named Gen. Fahd Jassem Al-Freij as the new defense minister. Al-Freij used to be the army chief of staff. Republican Guard troops surrounded the nearby Al-Shami Hospital, where some officials were taken for treatment, witnesses said. Whether the explosion was part of a broader rebel offensive in the capital was not clear. At least one rebel leader has declared that the “liberation” of Damascus was in progress. But the scattered violence and skirmishes do not necessarily suggest a coordinated series of attacks against Assad's security forces. News of the bombing was greeted with joy in Jabal Shahshabu, a rebel stronghold in central Syria where people fired Kalashnikov assault rifles into the air and shouted “Allah-o-Akbar” (God is Greatest). Columns of black smoke rose over Damascus as troops shelled Qaboon and Barzeh, while fighting raged in Al-Midan and Zahira and loud explosions were heard in Mashrou-Dumar, said the Local Coordination Committees. The observatory said violence across Syria had killed at least 100 people so far on Wednesday, among them 19 people in Damascus, including the security chiefs. All but one of the rest were civilians. White House National Security Council spokesman Tommy Vietor said Assad was “losing control,” pointing to “increasing” defections and a “strengthened and more united” opposition. Pentagon chief Leon Panetta said the international community must “bring maximum pressure on Assad to do what's right, to step down and to allow for that peaceful transition.” Russia demanded the arrest and strict punishment of those behind what it called an “act of terror.” “We see the events as another attempt to further destabilize the situation in Syria,” the foreign ministry said, calling on both sides to reassess the situation and seek peace. However, the Kremlin said Russian President Vladimir Putin and US counterpart Barack Obama were unable to resolve their differences on Syria in a telephone conversation. “Differences in approaches remain that concern practical steps in achieving a settlement,” Kremlin spokesman Dmitry Peskov was quoted as saying by Russian news agencies. In the wake of the bomb attack, the UN Security Council delayed a vote on a resolution that would threaten sanctions against the Syrian leadership. UN and Arab League envoy Kofi Annan requested the delay, which was granted by the resolutions' Western sponsors, diplomats said. The West and Russia are headed for a showdown on a resolution that would extend the mandate of the UN's unarmed observer mission in Syria, which expires Friday. The West insists the resolution must contain a threat of sanctions against the Syrian leadership or it may let the mission expire — a maneuver Moscow has called “blackmail.” “Adopting a resolution against this backdrop would amount to a direct support for the revolutionary movement,” Russian Foreign Minister Sergei Lavrov said in Moscow. “If we are talking about a revolution then the UN Security Council has no place in this.'' Hague's warning Syria is tipping into chaos and collapse, and a strong UN Security Council stand is needed to push for the creation of a transition government, British Foreign Secretary William Hague said. “It is clear that the situation is deteriorating rapdly,” Hague told reporters during a visit to Lithuania. – Agencies