CAIRO — Growing in confidence after eight months in power, Egypt’s military generals appear more determined than ever to crush the protest movement that ousted Hosni Mubarak and has turned critical of their rule.

This week, they detained Alaa Abdel-Fattah, a blogger whose activism made him an icon of the anti-Mubarak uprising, and — in an accusation that was derided by fellow activists — said he was to blame for stirring up violence at an October protest where 27 people were killed when soldiers cracked down.

At the same time, the military leadership has been drumming up an image of itself as the nation’s foremost patriots, even as it steps up moves to silence critics, leaning on managers of media outlets to tone down commentary on the army or ban particularly vocal critics from appearing on political talk shows.

Activists worry the military aims to hold power for as long as possible to give itself time to create favorable conditions for one of its own or a civilian with military background to run for president in elections. In what many saw as a trial balloon, posters went up briefly last week in Cairo voicing support for the head of the military, Field Marshal Hussein Tantawi, as a presidential candidate.

Tantawi and other generals on the ruling Supreme Council of the Armed Forces insist the military has no wish to stay in power and will not field a candidate in the presidential election, slated for late next year or early 2013. But activists doubt it will willingly give up the domination it has enjoyed over the nation for decades.

“I have serious doubts that the military will hand over power to civilians,” said activist Ahmed Imam. “They will most likely choreograph a scenario in which they will appear to hand over power but will in fact hold on to power.”

The arrest of Abdel-Fattah has fueled accusations that the military is trying to sweep away the taint its reputation suffered from the bloodshed at the Oct. 9 protest that turned into Egypt’s worst violence since Mubarak’s fall in February. Troops stormed the protest outside the state television building. Video from the scene showed military armored vehicles barreling through crowds and soldiers heavily beating and firing on protesters.

The military later blamed the Christians and “hidden hands” for instigating the violence, denying its soldiers had live ammunition.

On Sunday, the military ordered Abdel-Fattah held for questioning for 15 days on suspicion of inciting the rioting, damaging military property and assaulting on-duty troops. If charged, he could face trial before a military court, where thousands of protesters and other civilians have been prosecuted in recent months — many ending with swift and harsh verdicts.

At least 3,000 people marched through downtown Cairo on Monday to protest Abdel-Fattah’s arrest, chanting “Down, down with military rule” and “Alaa, we’re behind you, don’t stop.” Abdel-Fattah, 29, was Egypt’s first blogger activist, launching a blog years ago organizing opposition to Mubarak. He has been a vocal critic of the military’s rule since Mubarak’s ouster.

“They want to hide the actual criminals,” rights lawyer and activist Gamal Eid said.