In the thick of charcoal smoke rising from kebab grills in downtown Lagos, traders and their customers excitedly talk up Nigeria's chances ahead of the country's first World Cup knockout match in 16 years.

But the optimism is tempered by disquiet -- if not outright fear -- that a worsening Islamist insurgency raging in the north could make its way to the west African nation's biggest city at any time.

"We are worried in Lagos for sure. People should be worried because seeing and hearing from other states what is happening, one has to be very conscious," said Femi Adeeko, 66, who runs the Famoss Hotel, in the city's affluent Ikoyi district.

Nigeria hopes to become the first African side in World Cup history to make it to the semi-finals, but they face a tough route, with European powerhouses France first in the firing line.

Hopes are sky high after a creditable performance against Argentina in the group stage where, despite losing 3-2, Nigeria won over many critics and CSKA Moscow forward Ahmed Musa became an overnight hero after netting twice.

But preparations have been overshadowed by an attack on Sunday by suspected Boko Haram Islamists on a series of churches in northeastern Nigeria, with at least 50 dead, just days after a shopping centre was bombed in the capital Abuja.

Defying advice from the police to avoid public viewing centres, crowds were already gathering in Lagos bars before midday ahead of the 5:00 pm (1600 GMT) kick-off in the France game.

In the sprawling Obalende market in Ikoyi, the din of generators drowned out the on-screen chatter of the pundits as fans crowded around screens to watch the pre-match build-up.

The 1960Bet bookmaker in Obalende market, where a gleaming green and white flag of Nigeria dominated the crumbling facade, was offering odds of 4.25-1 against Nigeria progressing to the quarter-finals.

"This is the southwest, the most peaceful region. We are free here. Of course we are worried about our brothers in the northeast but we are not concerned here," said manager Binuyo Lewis, 35.

Lewis said punters were heavily backing the Super Eagles despite France being the overwhelming favourites to go through.

"Of course we will win the match. We will defeat the French. Hopefully it's going to be 2-1 in favour of Nigeria. I'd say my man Musa is going to score," he told AFP.

At bar and hotel a five minute walk through deep, muddy puddles collecting outside stalls selling pirate DVDs, traditional medicines and barbecued lamb, Faseun Olasupo and his staff wiped tables and checked stocks ahead of an expected rush of business.

"We are expecting a lot of people. We played very well against Argentina and people think we can play better against France. I think it will by 2-0. Musa and Ozase will score," he said, using the local name given to Musa's strike partner, Stoke City forward Peter Odemwingie.

"People are not talking about Boko Haram here. There is no concern here."

France thrilled in their first two group games, beating Honduras 3-0 and crushing Switzerland 5-2. Although a much-changed side then drew 0-0 with Ecuador, they find themselves being discussed as potential champions.

Bookmaker Steven Souji, 35, said that although support for the Super Eagles had been strong throughout the tournament, some people were less confident of a win.

"Most people who come in here are betting on Nigeria but a few of them are supporting France."