BEIRUT, Lebanon — More than 50 people were killed in bomb, mortar and rocket attacks in government-controlled areas of Syria on Tuesday, as the international chemical weapons monitoring group declared that it was sending inspectors to the country to investigate suspected use of chlorine gas.

The wave of attacks on civilian, mainly pro-government, areas in the capital, Damascus, and in the central city of Homs, came a day after President Bashar al-Assad formally announced plans to run for re-election. Taken together, the day’s events underscored the uncertainties around the elections planned for June 3, which government opponents widely regard as a sham, saying Mr. Assad’s victory is guaranteed.

It remains unclear how the vote can be carried out safely amid the war, while insurgents still strike in the heart of government territory and the government bombards insurgent-held areas in major cities like Aleppo on a daily basis.

While the government has aimed to gain a new measure of international credibility by pledging elimination of its chemical weapons program, it now faces new questions not only about the suspected chlorine attacks, but about its repeatedly missed deadlines — most recently on Sunday — to remove the declared toxic arsenal from the country.