BEIRUT (AP) — Syrian forces fired a barrage of mortar shells at an opposition stronghold Wednesday even as the foreign minister promised the regime would respect a week-old cease-fire and withdraw troops from urban centers in line with an international peace plan.

A troop pullback is a key provision of special envoy Kofi Annan's six-point plan to end 13 months of bloodshed in Syria, but the regime has ignored last week's deadline of getting tanks and troops off the streets.

Instead, Syrian soldiers continued to pound rebellious areas with artillery after an initial lull at the start the truce a week ago Thursday, raising growing international concerns that Annan's plan will fail.

In the latest violence Wednesday, activists said regime forces fired mortar shells at the central city of Homs, killing at least two civilians and sending thick gray smoke into the air as loud booms rang across residential areas.

The state news agency also said two separate roadside bombs killed 10 members of the security forces and a civilian in northern Syria. SANA reported that six soldiers were killed and 11 wounded in a blast in the village of Mastouma in Idlib province, while a second explosion in the Aleppo region killed four members of the security forces and a civilian.

The attacks were a sign that both sides have violated the cease-fire and could prompt the regime to intensify its assault on rebellious areas. Syria's government has portrayed the uprising as a foreign-led conspiracy by terrorists and thugs.

Despite persistent violence, the international community is reluctant to declare the cease-fire dead, in part because it is seen as the only way to end bloodshed triggered by an uprising against President Bashar Assad. As part of Annan's road map, a halt to fighting is to be followed by political talks between Assad and Syria's opposition.

Other options, such as foreign military intervention, arming Assad's opponents and economic sanctions, have either been discarded or offer no quick solution. A deadlocked international community would be hard put to offer an alternative if it were to acknowledge the collapse of the cease-fire.

Syrian Foreign Minister Walid Moallem insisted Wednesday that Syria is keeping its commitments. Syria will "continue to cooperate" with Annan's efforts, the Chinese Foreign Ministry quoted Moallem as saying after he met with his Chinese counterpart in Beijing.

Syria will "honor and implement Annan's six-point proposal, fulfill its cease-fire, troop withdrawal and other relevant commitments and begin cooperation with the U.N. monitoring team," Moallem said according to the statement.

China, Russia and Iran have been Syria's staunchest allies. U.N. Security Council members Russia and China have twice shielded the Assad regime from international condemnation, but also demanded that Syria comply with the Annan plan.

After Russian Foreign Minister Sergey Lavrov told Moallem last week that Syria could do better, his Chinese counterpart, Yang Jiechi, urged his Syrian visitor Wednesday to make the Annan plan work.

Yang said he hoped Syria would "actively cooperate in putting in place the cease-fire monitoring mechanism, and sincerely embark on a process of inclusive political dialogue and reform to bring about a just, peaceful, and appropriate resolution to the Syrian question."

Yang's remarks were more pointed than in past, an indication that Beijing is looking for progress toward a reduction of violence that might dilute some of the criticism China has come under for blocking U.N. action on Syria.

Meanwhile, U.N. chief Ban Ki-moon was intensifying efforts to get a large contingent of observers on the ground to salvage the truce. He said a team of 250 monitors, as originally envisioned, might not be sufficient for the job. He has also asked the European Union for planes and helicopters to make the mission more effective. Ban is to report to the Security Council on Wednesday.

Moallem said in Beijing that Syria would be ready to provide helicopters, but made no reference to Ban's request to the EU.

"Syria is ready to make its air force available for the use of this delegation," Moallem said. "As we have understood, what is needed are helicopters to evacuate the injured. If that is the issue, then we have the capabilities in our air force to carry this out."

An advance team of half a dozen observers has been in Syria since the weekend. On Tuesday, the team went on its first field trip to the southern city of Daraa where the activists reported protracted fighting between rebel gunmen and Syrian soldiers. On Wednesday, an explosion was heard in the city, followed by a gunbattle, said the Syrian Observatory of Human Rights, an activist group based in Britain.

The head of the team, Col. Ahmed Himiche, said Wednesday that he expects an additional two dozen monitors by Thursday. He said the team would be in touch with both sides in conflict, but did not comment on the trip to Daraa.

Rami Abdul-Rahman, the head of the Observatory, said he and other opposition activists support the truce plan despite widening regime attacks that have claimed dozens of lives in the past week. In Homs, battered by artillery for weeks, with just a brief respite last week, mortar shells fell every 10 to 15 minutes on Wednesday morning, he said. The Observatory said at least two civilians were killed.

"If the Annan plan fails, what happens?" Abdul-Rahman said. "There will be fighting between armed people and the Syrian army. Everyone loses .... Syria will disintegrate. The Annan plan is the last chance for us."

Separately, government-run Syrian television broadcast footage showing Assad and his wife Asma visiting an aid collection center for people displaced by the violence in Homs. The report, aired Tuesday, showed Assad and his wife being mobbed by cheering supporters as they entered the al-Fayha stadium where volunteers were collecting and packing aid donations.

Associated Press writer Scott A. McDonald in Beijing contributed reporting.