Two women – a Swiss and an Austrian – have been freed after more than a year in captivity in Niger and handed over to authorities in the Libyan city of Benghazi.

Austrian national Eva Gretzmacher, 76, and Swiss Claudia Abbt, 69, were kidnapped separately in the northern Nigerien city of Agadez in January and April last year.

No details have been given about who was holding them or their demands, although some reports have previously linked the kidnapping to Islamic State militants. The circumstances of their release were not disclosed.

The Austrian and Swiss governments have both confirmed the release of their citizens.

The Swiss government said Abbt was free and on her way back to Switzerland, while Austria said Gretzmacher had been released after “intensive diplomatic efforts”.

“We are all very relieved that Eva G. is free again after more than 21 months… For many months, we worked closely, discreetly, and in a spirit of trust with our regional, European, and international partners. These joint efforts have paid off,” Foreign Minister Beate Meinl-Reisinger said in a statement.

The Swiss foreign ministry said the country’s federal administration officials had met Abbt in Benghazi and she had received medical care.

“She is doing well under the circumstances and is currently on her way back to Switzerland,” it added.

Federal Councillor Ignazio Cassis thanked those involved in her release, adding that he was “relieved that [she] is free again after more than a year and a half”.

The government said it had established a task force – including the foreign affairs department, police and other agencies – after the kidnapping became known.

It added that Switzerland had maintained regular contact with Austria from the outset.