The police said in a written statement that a man with a homemade explosive had removed it from his backpack and dropped it in front of a check-in counter. The statement indicated that the explosive was contained in a beer bottle or bottles.

After the blast, “the man also took a knife from the backpack and slashed his own throat and fell to the ground,” the police said. The man survived but was said to be in grave condition.

In addition, a nearby hospital took in four casualties of the explosion who were lightly wounded by bottle fragments, the police said. One was a citizen of the Philippines.

By late Sunday afternoon, the airport was calm. Twelve of the next 18 flights scheduled to land were listed as delayed for as long as four hours. The cavernous departure hall of Terminal 2 was operating across two-thirds of its length, but Aisle C, where the explosion occurred, was roped off, and uniformed security personnel with black assault rifles slung over their shoulders stood guard, making it difficult to see any damage.

China’s Communist Party leadership prides itself on maintaining absolute control, and even relatively minor disruptions of that control can prompt an intense response. Hangzhou, a city near Shanghai, is scheduled to host a summit meeting of the Group of 20 leading economies in September.