COPENHAGEN, Denmark — Pirates have hijacked a Danish sailboat with four adults and three children aboard as they were crossing the Indian Ocean, Denmark’s government said today.

Most hostages captured in the pirate-infested waters off East Africa are professional sailors, not families. Pirates are not known to have captured children before.

The Danish Foreign Ministry said the ship sent a distress signal on Thursday. On board was a Danish couple, their three children — aged 12 to 16 — and two adult crew members, also Danes.

“It has now been confirmed that the sailboat was hijacked by pirates in the Indian Ocean,” the ministry said in a statement.

Two days before the Danish sailboat sent the distress signal, four Americans were killed by Somali pirates in a hostage standoff. They were the first Americans slain by Somali pirates since a wave of attacks began six years ago.

Danish Foreign Minister Lene Espersen said she was “deeply concerned” about the situation and expressed her sympathies to the Danes on the boat and their relatives.