DAMASCUS, Syria (AP) — Gunmen detonated back-to-back roadside bombs and clashed with police in central Damascus yesterday in attacks that caused no damage but highlighted the ability of rebels to breach the intense security near President Bashar Assad’s power bases.

The apparently co-ordinated blasts point to the increasing use of guerrilla-style operations in the capital to undermine the Government’s claims of having full control over Damascus. It also suggests that rebel cells have established a Damascus network capable of evading Assad’s intelligence agents and slipping through security cordons.

Assad’s regime, however, has displayed no hesitation on the battlefield despite blows such as the Damascus attacks and defections of high-ranking military and political figures, including the prime minister last week.

In Aleppo, activists said Syrian forces pressed ahead with an offensive to break rebel footholds in the nation’s largest city. The London-based Syrian Observatory for Human Rights said a helicopter gunship fired missiles on apartment buildings a day after protesters begged for international shipments of anti-aircraft weapons.

With diplomatic efforts all but exhausted, strategic planning has moved into high gear for Assad’s possible fall or worst-case scenarios if the civil war deepens, including use of his suspected chemical arsenal.

In Istanbul, US Secretary of State Hillary Rodham Clinton and Turkey’s foreign minister said their countries were creating a special joint task force to respond to potential crises such as victims of chemical attacks or a dramatic spike in the more than 200,000 refugees that have already fled Syria.

“We have been closely co-ordinating over the course of this conflict, but now we need to get into the real details of such operational planning. It needs to be across both of our governments,” Clinton said after talks with Foreign Minister Ahmet Davutoglu.

Davutoglu hinted at the possibility of setting up a so-called “safe zone” inside Syria to protect war refugees from possible attacks by Assad’s gunners or warplanes. “We need to brace for impact,” he said.

The Arab League, meanwhile, announced that its foreign ministers will meet in an emergency session in Jiddah, Saudi Arabia today to discuss the Syrian meltdown, which human rights groups say has claimed at least 20,000 lives. Some Arab states, led by Saudi Arabia and Qatar, are major rebel backers.

Syria’s security forces say they pushed the rebels from the capital after intense, week-long battles last month. But opposition fighters appear resilient and resourceful in some areas.

On the capital’s northern edge, Syrian forces pounded the suburb of al-Tal with mortars and artillery shells in the third consecutive day of government barrages, said Mohammed Saeed, an activist in al-Tal. He said they were using helicopters to strafe the area, adding that two hospitals were hit.

“The situation is very grave and the town is completely besieged,” he said.

It came a day after armed men snatched three journalists from the pro-regime TV station Al-Ikhbariya and their drivers while they were covering the al-Tal violence. The station’s general manager, Imad Sarah, said efforts were under way to release them. In June, gunmen raided Al-Ikhbariya’s headquarters, killing seven employees.

The bombings in Damascus itself brought chaos to some of the most exclusive areas of the capital in a symbolic blow to Assad.

One blast — from a device planted under a tree — was set off by remote control as a vehicle carrying soldiers passed by in the Marjeh district, an official at the site of the blast told The Associated Press, speaking on condition of anonymity because he was not authorised to talk to the press.

The explosion, which caused no casualties, was about 100 yards from the Four Seasons, one of the top luxury hotels in Damascus.

After the blast, gunmen opened fire on civilians “to provoke panic”, the state-run news agency SANA said.

At the same time, the second explosion went off near Tishrin Stadium, less than a half-mile away, SANA reported.

Just hours later, SANA reported that a bus was attacked in a Damascus suburb, killing six passengers travelling from the central province of Hama.

The news agency said security agents were pursuing the attackers in all incidents, referring to them as “terrorists” — the term authorities routinely use for rebels trying to topple Assad’s regime.

Explosions in the capital have become increasingly common as Syria’s civil war escalates. On August 18, rebels carried out a sophisticated bombing of a regime security building that killed four members of Assad’s inner circle.

Abductions, too, have been on the rise.

DAMASCUS, Syria — This image made from amateur video released by the Shaam News Network and accessed yesterday purports to show the destruction of houses by shelling from Syrian government forces in Damascus last Wednesday. (Photo: AP)