In fresh attacks on symbols of state power, twin suicide bombings occurred Monday near a government security compound in northern Syria and grenades hit the central bank in Damascus, killing nine people and wounding 100.

The regime and the opposition traded blame, accusing each other of dooming a United Nations peace plan that has largely failed. The head of the U.N. observer mission in Syria acknowledged that his force cannot solve the country’s crisis alone and urged both sides to stop fighting.

The attacks are the latest in a series of suicide bombings that started in December and have mostly targeted Syrian military and intelligence installations.

The regime routinely blames the opposition, which denies having a role in such attacks or the capability to carry them out. After other similar bombings, U.S. officials suggested that al-Qaeda militants may be joining the fray, and an Islamist group inspired by al-Qaeda has asserted responsibility for previous attacks in Syria.

The powerful blasts Monday, which blew two craters in the ground and ripped the facade off a multistory building, occurred a day after Maj. Gen. Robert Mood, the head of the U.N. observer mission, took up his post in Damascus.

“Ten, 30, 300 or 1,000 observers will not solve all problems,” he told reporters Monday. “So everyone has to help us achieve this mission.”

More than 9,000 people have been killed in the 13-month-old crisis, according to the United Nations.

An April 12 cease-fire agreement has helped reduce violence, but fighting persists, and U.N. officials have singled out the Syrian regime as the main aggressor.

An advance team of 16 U.N. observers is on the ground to try to salvage the truce, which is part of a broader plan by special envoy Kofi Annan to launch talks between President Bashar al-Assad and his opponents. By mid-May, the team is to grow to 100, but U.N. officials have not said when a full 300-member contingent is to be deployed.

On Monday, the suicide bombers struck in the northern city of Idlib, an opposition stronghold that government troops recaptured in an offensive earlier this year. Earlier Monday, gunmen fired rocket-propelled grenades at the central bank and a police patrol in Damascus, wounding four officers, according to the Syrian Arab News Agency.

U.N. Secretary-General Ban Ki-moon condemned “the terrorist bomb attacks” in Idlib and Damascus, U.N. deputy spokesman Eduardo del Buey said.

— Associated Press

AP writers Albert Aji in Damascus and Karin Laub in Beirut contributed to this report.