Syrian forces fired mortars and rockets on Thursday in the rebellious city of Homs, the latest salvo in a week-long assault that has killed hundreds as President Bashar Assad’s regime tries to crush increasingly militarised pockets of dissent.

As the violence grinds on, the international community is searching for new diplomatic approaches to stop the protracted bloodshed in Syria.

A senior Arab League official said on Thursday that the Cairo-based organisation will discuss at a meeting next week whether to recognise the opposition Syrian National Council as the legitimate representative of Syria and whether to allow it to open offices in Arab capitals.

The official spoke on condition of anonymity because no decision has been made on the issue. Foreign Ministers from the 22-member Arab league are scheduled to meet in Cairo on Sunday.

In the latest operation, which began on Saturday, government forces have unleashed a relentless offensive against Homs, shelling residential areas as they try to root out any resistance and retake control of the city of a million people.

The Britain-based Syrian Observatory for Human Rights said at least 20 people were killed on Thursday, but an exact death toll couldn’t be determined because of the chaos in the city.

Also on Thursday, Germany expelled four Syrian diplomats following the arrest earlier this week of two men accused of spying on Syrian opposition groups in the country.

Foreign Minister Guido Westerwelle said he ordered the expulsions of the four Syrian Embassy employees and the ambassador had been informed. He did not give details on the diplomats.

German federal prosecutors said on Tuesday they had arrested a Syrian and a German-Lebanese dual national on suspicion that they spied on Syrian opposition supporters in Germany over several years.

The uprising began with mostly peaceful protests, but it has transformed into an armed insurgency against Assad in many areas.

The U.N. estimates that 5,400 people have been killed in Syria since the uprising began in March. But that figure is from January, when the U.N. stopped counting because deteriorating security prevented verification of the figures.

U.N. Secretary-General Ban Ki-moon said on Wednesday the head of the Arab League plans to send observers back into Syria and has raised the possibility of a joint mission with the United Nations.

The U.N. chief provided no specifics, but the idea appears aimed at giving the regional group a boost after the league’s earlier mission was pulled out of the country because of security concerns.

“In the coming days we will further consult with the council before fleshing out details,” Mr. Ban said. “We stand ready to assist in any way that will contribute toward improvement on the ground.”

Mr. Ban also reiterated his “deep regret” over the council’s inability to speak in one voice to stop the bloodshed. Russia and China used their veto powers on Saturday to block a Security Council resolution backing an Arab League peace plan that calls for Assad to step aside.

Mr. Ban said the lack of council unity has encouraged the Syrian government to step up its attacks on civilians.

“Thousands have been killed in cold blood, shredding President Assad’s claims to speak for the Syrian people,” Mr. Ban said. “I fear that the appalling brutality we are witnessing in Homs, with heavy weapons firing into civilian neighbourhoods, is a grim harbinger of worse to come.”

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