Nigeria was on high alert Monday after the United States warned of fresh attacks following a wave of deadly blasts claimed by Islamists 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.
The US embassy said potential targets could include the Nicon Luxury, the Sheraton and the Transcorp Hilton, Abuja's premier hotels.
Embassy staff had been told to avoid the venues and US citizens urged to exercise "additional caution".
In addition to the normal in-house security checks, police were also deployed to the hotels, while armed soldiers stopped and searched cars driving close to the hotels and the central bank in the capital.
Some 13,000 policemen and specialist anti-terror squads were deployed to mosques and churches and other strategic locations across the city on Sunday, a police official 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".
National police spokesman Yemi Ajayi said: "Everywhere is closely monitored, we don't want to take chances, particularly in Abuja."
An Abuja-based western diplomat 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, or the Feast of Sacrifices prayers at an open ground patrolled by dozens of armed police.
Celebrations in the sleepy city were low key and on Monday its streets were almost deserted and businesses shut.
People are struggling to strike a balance between the merriment of the season and the losses the city has incurred from the attacks, especially the large number of people that have been killed," Aisami Bundi, a resident, said.
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.
"It is a period that we are all expected to live in peace but as a nation we have our own challenges, even during this holy period we still have incidents happening here and there," he said.
While churches and police were among the initial targets, gunmen fired indiscriminately in the streets. Muslims and Christians alike were among those killed.
"The attack seems to have been haphazardly carried out which explains the heavy toll. Both Muslims, Christians, civilians, soldiers, policemen and other paramilitary personnel were all part of the casualties," said Ibrahim Farinloye, a spokesman for Nigeria's emergency management agency.
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 sect, which wants to see the establishment of an Islamic state in northern Nigeria, staged an uprising which was brutally put down by security forces in 2009.
Nigeria's more than 160 million people are divided almost in half between Muslims and Christians, living roughly in the north and south of the country respectively.