Geneva- The United Nations was marking Tuesday the 50th day that John Solecki, who worked for the organization in Quetta, Pakistan, was being held in captivity.

Solecki was abducted on February 2 this year, in an attack that killed another UN staff member. His health was said to be deteriorating and the UN was worried about his medical condition.

Currently, 19 UN staff members are under arrest, detained or missing, around the world, said UNHCR, the refugee agency that employs Solecki.

On Wednesday the UN will commemorate the International Day of Solidarity with Detained and Missing Staff members.

Attacking aid workers "hurts all of us, but especially the most vulnerable," the agency said in a statement.

A shadowy secular rebel group Balochistan Liberation United Front (BLUF), which said it captured Solecki, extended earlier this month "indefinitely" a deadline for killing the UN official.

The BLUF has demanded the release of more than 1,100 political prisoners for the release of Solecki, an American national, who is being held in Pakistan's south-western Balochistan province. (dpa)