By Tom Perry and Shadia Nasralla
CAIRO (Reuters) - Egypt increased pressure on the Muslim Brotherhood on Thursday, detaining at least 38 of its supporters on suspicion of belonging to a terrorist organization the day after it was declared one by the government, security officials said.
General Abdel Fattah al-Sisi, the army chief who led the overthrow of Islamist President Mohamed Mursi in July, said the country would be "steadfast" in the face of terrorism, after a small bomb went off in Cairo, wounding five people.
The government declared the Muslim Brotherhood a terrorist group on Wednesday in response to a suicide attack a day earlier that killed 16 people in the Nile Delta, accusing the group of carrying out the bombing. The Brotherhood, which claims up to 1 million members, condemned the attack.
The move gives the authorities wider scope to crack down on the movement that propelled Mursi to the presidency 18 months ago but has been driven underground since the army toppled him.
Sixteen of the arrests were in the Nile Delta province of Sharkiya. The state news agency said those held were accused of "promoting the ideology of the Muslim Brotherhood group, distributing its leaflets, and inciting violence against the army and police". Security sources gave a country-wide total of 38 arrests on terrorism charges.
From now on, anyone taking part in Brotherhood protests will be jailed for five years, Interior Ministry spokesman Hany Abdel Latif told state TV. Jail terms for those accused under the terror law stretch up to life imprisonment. "The sentence could be death for those who lead this organization," he said.
Terrorism charges will also apply to anyone who finances or promotes the group "verbally and in writing". Publication of the Brotherhood's newspaper, Freedom and Justice, was halted in response to the decision.
The state has accused the Brotherhood of turning to violence since the army toppled Mursi after mass protests against his rule. Since then, attacks on the security forces have become commonplace, with around 350 soldiers and policemen killed.
The Brotherhood denies turning to violence, saying the army has mounted a bloody coup and killed hundreds of its supporters.
ONE BOMB GOES OFF, TWO OTHERS DEFUSED
The government says it will stick to its political transition plan. The next step is a mid-January referendum on a new constitution, after which elections will follow.
Sisi is widely tipped to win a presidential election expected next year, assuming he runs.
Some analysts believe the nation of 85 million people faces a protracted period of Islamist militancy, with attacks spreading beyond the restive Sinai Peninsula, the scene of the worst violence against the security forces to date.
The government has yet to make public any evidence to back up the charge that the Brotherhood staged the Nile Delta attack on a police station in Mansoura, north of Cairo.
The attack was claimed by the Sinai-based radical Islamist group Ansar Bayt al-Maqdis. Ansar Bayt al-Maqdis has taken responsibility for several other major bombings, including a failed attempt to kill the interior minister in September.
The small bomb that went off in Cairo smashed the windows of a bus. Abdel Latif said a second similar home-made device was found nearby and dismantled. The state news agency reported that the security forces had thwarted an attempt to set off a bomb outside a police compound in Kafr el-Sheikh province.
The Interior Ministry said it will secure polling stations for next month's referendum by deploying secret police, combat units and explosives experts, according to a statement.
It said it would boost security at churches before January 7, when Coptic Christians, who make up about a tenth of the population, celebrate Christmas.
The Interior Ministry has opened three telephone lines for citizens to report suspected terrorist activities, including those by the Brotherhood, an official said.
The Brotherhood's Islamist allies responded defiantly to the cabinet decision, vowing to continue protests.
"The putschists are a terrorist organization. The Brotherhood are peaceful patriots," they said in a statement.
In the weeks after Mursi's removal, the security forces killed hundreds of his supporters while dispersing their protest camps, and arrested thousands more, including most of the Brotherhood's top leadership.
State prosecutors last week ordered Mursi and others to stand trial on charges including terrorism and conspiring against Egypt. They could face the death penalty.
The National Alliance to Support Legitimacy, the pro-Mursi coalition, called for a "week of anger" over the decision.
The public prosecutor's office, which is investigating the Mansoura bombing, said there would be no comment until its investigation was complete.
(Editing by Mark Trevelyan)