Nigeria was on high alert after the United States warned of fresh attacks following a wave of deadly blasts claimed by Islamists that killed 150 people in the northeast of the country.
Friday's attacks in the city of Damaturu were among the deadliest ever carried out by Boko Haram, an Islamist sect based in the north of Africa's most populous country.
The US embassy in Nigeria warned the sect could next strike hotels and other targets in the capital Abuja during the Muslim holiday of Eid al-Adha.
"Following the recent Boko Haram, aka Nigerian Taliban, attacks in Borno and Yobe State, the US embassy has received information that Boko Haram may plan to attack several locations and hotels in Abuja," the embassy said.
Security was stepped up in Abuja, which has been a target of past attacks, including an August 26 suicide bomb at the UN headquarters which claimed 24 lives.
Embassy staff were told to avoid the venues and US citizens were urged to exercise "additional caution".
As well as normal in-house security checks, police were also deployed to the hotels, while armed soldiers stopped cars driving close to the hotels in the capital and searched their bonnets and trunks.
The country's state security services played down the latest threat, arguing that police had been on high alert for three months.
"The current threat of attack on the three hotels in Abuja is not news, and for over three months the security services have taken pro-active measures to protect the designated critical facilities and others," the president's security advisor, Andrew Azazi, said in a statement.
Some 13,000 policemen and specialist anti-terror squads were nevertheless deployed to mosques and churches and other locations across Abuja on Sunday, police officials said.
Worshippers were screened by metal detectors before they entered some churches.
The British Foreign Office on Sunday also warned of "a heightened threat of terrorist attacks during the Eid ... weekend across northern states in Nigeria."
It advised British nationals to maintain a "high level of vigilance."
Police have been placed on red alert. "We don't want to take chances, particularly in Abuja," said national police spokesman Yemi Ajayi.
A Western diplomat in the capital said: "Obviously what happened in the last few days, and the US warning, has called for extra monitoring."
In the grief-stricken city of Damaturu where the 150 died, thousands of Muslims gathered for Eid el-Adha prayers at an open ground patrolled by dozens of armed police.
Celebrations in the sleepy city, which is under a curfew, were low key and on Monday its streets were almost deserted and businesses shut. Some people went to a hospital morgue to collect the remains of their loved ones for burial.
President Goodluck Jonathan, who described the wave of gun and bomb attacks in the capital of Yobe state as "heinous", appealed to Muslims to pray for peace as they marked Eid, which ended at sundown on Monday.
Ekmeleddin Ihsanoglu, chief of the world's largest pan-Islamic body the Organisation of Islamic Cooperation, "strongly condemned the terrorist attacks" describing them as "criminal ... contrary to all human values and the noble Islamic values."
EU foreign policy chief Catherine Ashton sharply condemned the "brutal attacks" adding: "Such mindless and heinous acts cannot under any circumstances be justified."
While churches and police were among the initial targets, gunmen fired indiscriminately in the streets. Muslims and Christians alike were among those killed.
Militants from Boko Haram, whose name means "Western Education Is Sin" in the regional Hausa language, have in the past targeted police and military, community and religious leaders, as well as politicians.
The latest attacks point to the group's growing determination to take on the government.
"The truth of the matter is we are (now) faced with armed insurgency," said northern-based rights activist Shehu Sani, of the Civil Rights Congress group.
Boko Haram has claimed to be fighting for the establishment of an Islamic state in Nigeria, whose 160 million population is roughly divided in half between Christians and Muslims.
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