Kassim Segawa prayed inside his local mosque near Uganda's capital but, instead of being in the company of scores of the faithful, on this day he was alone.

A crackdown by Ugandan police on suspected Islamic extremists has sent a current of fear through the Islamic community, especially in the Masjid Taqwa mosque whose imam — a former Guantanamo Bay prisoner — was recently arrested.

"I am a brave man to come here to pray today," said Segawa after he rose from the carpets and mats on the floor of the Masjid Taqwa mosque, a nondescript building on the edge of a slum, stepped outside and slid the lone pair of sandals onto his feet. "We are living with a lot of fear these days."

The crackdown was precipitated by the murder on March 30 of a top Ugandan prosecutor who was the lead prosecutor in the case of a dozen men accused of bombing two sites where soccer fans had gathered to watch the 2010 World Cup final. Al-Shabab, the Somali Islamic extremist group, claimed responsibility for that attack which killed at least 70 people.

The imam of the Masjid Taqwa mosque, the former Guantanamo Bay detainee named Jamal Kiyemba, was arrested earlier this month on suspicion of being involved in the shooting death of prosecutor Joan Kagezi. He is one of about 30 people, mostly Muslim men and women who lived in different parts of Kampala, Uganda's capital, who have been arrested in the case but not formally charged in court.

Kiyemba was deported to Uganda in 2006 after being freed from Guantanamo Bay, where he was held after being arrested while trying to enter Afghanistan. Some who know him describe him as a quiet, kind man who donated money to the sick and taught the Quran to new members of his mosque.

Ladislaus Rwakafuuzi, a prominent human rights lawyer in Uganda, said the police are profiling some Muslims and that he knows of an entire family that has been taken into custody as suspected extremists.

"Many people have been targeted because of their religion, not necessarily because of what they have done," he said.

Ugandan police deny unfairly targeting some Muslims. At least 12 million of Uganda's 36 million people are Muslims, according to government figures. Christianity is the predominant religion.

Police initially said al-Shabab, which opposes Uganda's military involvement in Somalia, may have killed the prosecutor. But without a claim of responsibility from al-Shabab, Ugandan authorities now say they are investigating many possible suspects, including a Congo-based, Ugandan-led Islamic extremist group known as Allied Democratic Forces.

Despite many terror warnings over the last few months, Uganda has avoided the frequent al-Shabab attacks seen in neighboring Kenya, which, like Uganda, is a target for contributing troops to a peacekeeping mission in Somalia. Ugandan police say they have foiled many attacks here over the years.

Segawa, the Muslim man who was praying alone in the Masjid Taqwa mosque, said the arrest of Kiyemba had left many of those who normally attend the mosque worried that they might be next. The 46-year-old, who drums up business for a taxi company, wears a long, scraggly beard even though some friends advised him to shave to avoid unnecessary attention from the police.

"The actions of the police are bad," he said. "They just arrest you without any evidence, in front of your family, and take you into custody and ask you what you have done."

Isma Kizito, a 28-year-old motorcycle taxi driver who sometimes prays at Kiyemba's mosque, said the mosque's muezzin no longer sounds the call to prayer. An elderly man, the muezzin reportedly went into hiding after Kiyemba was arrested.

"Sometimes you come here and the mosque is closed," Kizito said angrily. "It means that the Muslims no longer come. I feel bad about this."