Nigeria's army says soldiers have arrested 63 people in raids as they searched for the finance minister's 82-year-old mother, kidnapped from her home on Sunday.
It was still not known whether the abduction of Kamene Okonjo, mother of former World Bank director Ngozi Okonjo-Iweala, in Delta state, was political or for financial gain.
"Yesterday the Four Brigade raided Ogwashi-Ukwu in search of Mama," army spokeswoman Roseline Managbe told Reuters.
"Those arrested are being questioned," she added.
Africa's top oil producer has one of the world's most prolific kidnapping industries, yet Sunday's abduction shocked even residents of Delta state, thought to be Nigeria's worst.
Managbe said two Lebanese men working for Nigerian construction company Setraco had been abducted on Tuesday in Delta state by gunmen who killed a soldier protecting them.
Residents of the Niger Delta oil region, where Okonjo-Iweala's mother was abducted, live in fear of the near daily abductions that make millions of dollars in ransoms for gangs.
"It could be my turn tomorrow," said Tony Agwu, who lives near Okonjo's house.
"It's a terrible situation down here. The security agents in the Delta are compromised," he added, voicing the widely held view that security forces are often complicit.
The police said on Wednesday that two policemen have been arrested on suspicion of helping kidnappers.
Nigerians say December is the most dangerous month for kidnapping, when criminals need money to buy Christmas presents. The delta is no exception.
"Around this time, I start to get worried," said Shopia Oko-Akoko, a civil servant and mother of two in Bayelsa state, adding that she often looks over her shoulder entering her car.
"Many times I've seen cars following me. Once someone followed me on foot and I ran off in terror as he approached."
Okonjo's kidnapping is a risky strategy for the abductors.
"If it's just a kidnap for ransom, then they're not the smartest boys in the world," said Peter Sharwood-Smith, Nigeria country manager of security firm Drum Cussac.
"Everybody else learned that you don't pick the most high profile. It's not worth it. This might not end well for them."
Nigerian forces have little tolerance for kidnappers, whom they often shoot on sight when they catch them - as they did in November to 13 people suspected of abducting a Turkish man.
Cases of kidnapping in the Niger Delta exploded in around 2006, during the years of militancy by armed groups often targeting expatriate oil workers. An amnesty in 2009 officially ended militant activity, yet associated crimes, like oil theft from pipelines and abduction, have, if anything, worsened.
"Kidnapping is worse than during the militancy period, but it's mostly rich Nigerians who pay up and you never hear about it," Sharwood-Smith said.
Political motives have been suggested for the abduction. Ngozi Okonjo-Iweala's drive to reform a corrupt economy ruffled powerful vested interests, especially fuel importers.
A security source in Delta state said Okonjo was involved in local politics and seizing her may have been a scare tactic.
Either way, recruiting kidnappers is easy in a region where oil wealth sits along side mass unemployment.
"Whatever the motive, the main cause is joblessness," said Felix Osaduwe, a student in Delta state. "Get them jobs in a bank or a firm, there's no way they'll turn to kidnapping."