Nigeria: Boko Haram blamed for Maiduguri bombings
Four bombs have exploded in Maiduguri in north-eastern Nigeria, killing at least three people.
Two blasts went off at a hotel and one at a transport hub on Sunday night. There was a fourth blast at a cattle market on Monday morning.
Similar attacks have been blamed on the Islamist Boko Haram sect which has been battling security services in the city.
The latest bombings come ahead of polls on Tuesday for the governors of Nigeria's 36 states.
Unrest swept across Nigeria's north following a presidential election on 16 April, which was won by incumbent Goodluck Jonathan, a southerner. Hundreds of people are believed to have been killed and tens of thousands fled their homes.
Police said the bombs bore all hallmarks of Boko Haram, which has mounted almost daily attacks and killings in the city in recent months.
Correspondents say Boko Haram's grievances are entirely separate to the post-election violence, but there are also suspicions that the group has been used locally by politicians to attack and to intimidate voters.
Police say three people died, including a police officer, at the explosions at the Tudu Palace hotel's bar and 14 people were wounded.
The BBC's Bilkisu Babangida, in Maiduguri, says a police officer was also wounded in the explosion at the city's cattle market on Monday morning.
On Sunday, a three-page statement from Boko Haram, a group which is opposed to Western education and wants to see Islamic law imposed across Nigeria, was left outside of a newspaper office in the city warning of further attacks, our correspondent says.
"We will never accept any system of governance apart from the one described by Islam because that is the only way Muslims can be liberated," it said.
"We do not respect the Nigerian government because it is illegal. We will continue to fight its military and police because they are not protecting Islam."
There were two explosions in Maiduguri ahead of presidential polls, although no injuries were reported at the time.
Violence has also marred the election campaign in Borno state, including the assassination in January of the opposition All Nigeria People's Party (ANPP) candidate.
But our reporter says the latest bombings come as a surprise, as security is tight in the city because of the elections for governor.
"From all indications, this is the handiwork of Boko Haram, which has carried out similar attacks in the past," police spokesman Mai Mamm told AFP news agency.
Clashes in Maiduguri between Boko Haram and the police in July 2009 left hundreds of people dead, mainly member of the sect.
For the past six months, sect members have been fighting a guerrilla war, killing policemen and people they believe helped the security services in the fight against them.
Jibrin Ibrahim, political analyst at the Centre for Democracy and Development in Abuja, says Boko Haram has been arming itself for some time and is consciously trying to disrupt the polls.
"Elections are a demonstration of Western modernity which it is against," Mr Ibrahim told the BBC's Focus on Africa programme.
"Secondly it holds certain members of the political class responsible for the attempt to wipe them out a couple of years ago."