GULU, Uganda — President Omar Hassan al-Bashir, the authoritarian leader of Sudan wanted on genocide charges in connection with atrocities in Darfur, has been ousted by his nation’s military after nearly four months of mass protests shattered his grip on the country.

The nation’s defense minister, Lt. Gen. Awad Mohamed Ahmed Ibn Auf, announced on Thursday that Mr. al-Bashir had been taken into custody, the government had been dissolved and the Constitution had been suspended. He said there would be a two-year transition period, with the military in charge, and announced a 10 p.m. curfew.

Mr. al-Bashir, 75, who ruled Sudan longer than any other leader since the country gained independence in 1956, has long been regarded as a pariah in the West and as a ruthless strongman by many in his country.

He presided over massacres in southern Sudan, where his forces pushed barrel bombs from planes onto remote villages, and in Darfur and the Nuba Mountains, where hundreds of thousands died. In the 1990s, he hosted Osama bin Laden, pushing his country toward international isolation and American sanctions.

Before the announcement of his removal, protesters demanding Mr. al-Bashir’s ouster had gathered outside the military’s headquarters in Khartoum, the capital. They addressed a chant to the president: “You’ve been dancing for 30 years. Today it’s our turn to dance.”

“He has been such a burden for us,” said one 25-year-old protester who has lived his entire life under Mr. al-Bashir’s rule. “We can’t wait to build the new Sudan with freedom, justice and peace.”

But protesters’ jubilation was tempered by a wary uncertainty about what would happen after Mr. al-Bashir was toppled, given that the military said it was taking control.

“What has been just stated is for us a coup, and it is not acceptable,” said Sara Abdelgalil, a spokeswoman for the Sudanese Professionals Association, which has been organizing the protests. “They are recycling the faces, and this will return us to where we have been.”