A retired Nigerian army general who had been kidnapped by gunmen in the country's north-west has died while being held captive, the military has said.

Maj Gen Rabe Abubakar, who had a high-profile job as military spokesman between 2015 and 2017, was abducted with his wife while travelling in Katsina state last month.

No group has said it was behind the kidnappings.

The abduction and death of Abubakar highlights the continuing security challenges facing parts of north-west Nigeria, where criminal gangs known locally as "bandits" frequently carry out kidnappings for ransom, as well as cattle rustling and attacks on rural communities.

The Katsina state government said Abubakar died from natural causes.

The state's Internal Security and Home Affairs Commissioner, Nasiru Mu'azu, expressed regret over what happened, despite what he called "the relentless and concerted efforts" of both the state government and various security agencies to secure the general's safe release.

"The retired general died a natural death from complications of diabetes and hypertension,” he told reporters while expressing his condolences.

Meanwhile, the late soldier's family has called on the authorities to intensify efforts to rescue his wife, who is still with the kidnappers.

Abubakar's daughter, who spoke to the BBC, said the death of the retired military officer has placed the family in unbearable pain.

"The pain is unbearable. Only God will deliver us. We are praying. Allah is our only safety. By God's grace, we will be saved," she said.

Apart from bandits, militant jihadists have also operated in the region. An alleged militant camp in Sokoto state was the target of a US airstrike on 25 December last year.

Katsina has been one of the states most affected by the violence.

Local media reported that the retired officer had been going to a wedding on 30 May when armed men attacked his vehicle and seized him, his wife and their driver.

Days before news of his death emerged, a video shared on social media appeared to show Abubakar in captivity. He was seen with an apparent injury to his left leg alongside his wife and other hostages.

The military said it chose not to comment publicly on the abduction while efforts to free those in captivity were being made.

"In deference to ongoing rescue efforts by security agencies, the Armed Forces withheld public comment while every operational resource was deployed in the hope of securing his safe return," the statement said.

The whereabouts and condition of Abubakar's wife remain unknown. But a military spokesman said that "ongoing operations have since been further intensified to bring perpetrators to justice and to dismantle all terrorist networks threatening our nation".

The military paid tribute to the major general, who local media reported was 61 when he died, describing the loss as "tragic" and offered condolences to his family and former colleagues.

A statement said he made "immense contributions to counter-insurgency operations… His commitment to duty and to the unity of Nigeria remains a shining example for all personnel."