A suicide blast went off at a busy intersection in the Syrian capital Friday, killing 25 people and wounding at least 46 others.

Syrian state media say an attacker blew himself up near a school and police station in the central district of Midan in Damascus.

A bus carrying policemen appeared to be the target of the attack.

State television showed people carrying human remains, and others shouting the blast was the work of terrorists. The footage also showed damaged vehicles, including what appears to be a police bus with shattered windows and blood in it.

No one has claimed responsibility for the attack, which comes two weeks after twin blasts targeting security buildings in Damascus killed 44 people.

Meanwhile, there is mounting criticism about the effectiveness of an Arab League mission in Syria that is monitoring President Bashar al-Assad's compliance with a plan to end a bloody, 10-month crackdown on protesters.

On Thursday, Qatar's prime minister admitted the Arab League mission has made mistakes.

Syrian activists are calling for huge protests Friday in support of international aid.

Qatar's Sheikh Hamad bin Jassim al-Thani said U.N. aid is needed to improve the monitoring of Mr. Assad's government. He chairs the Arab League committee on Syria.

The Arab League will meet in Egypt on Sunday to assess the mission's initial findings in Syria and to decide whether it will continue. The initial 50 observers arrived on December 26 to monitor the Syrian government's compliance with a plan to end the violence.

The Arab League effort is aimed at ensuring Mr. Assad follows through on his pledge to withdraw security forces from cities, release political prisoners and allow anti-government demonstrations.

The United Nations estimates that 5,000 have died since the uprising began in March. But the global activist group Avaaz says it has verified through multiple independent sources that nearly 7,000 people have been killed in the Syrian unrest.