Another child has tested positive for the deadly bird flu virus which has already killed four children in Turkey, the health ministry said on Tuesday.

The latest case brings the total number of confirmed H5N1 cases among humans in Turkey to 21 over the past two weeks, including the four deaths.

The ministry said the child had tested positive while undergoing checks in the eastern Turkish city of Erzurum. Like the four people who died, the infected child comes from the town of Dogubayazit near the Iranian border.

Samples of the child´s tissue have been sent to a laboratory in London for further tests, the ministry said.

Prime Minister Tayyip Erdogan said on Tuesday five patients with H5N1 had recovered and had been discharged from hospital.

Many of the remaining 12 people are reported to be stable, but doctors said on Tuesday the condition of Muhammet Ozcan, the five-year-old brother of a girl who died on Sunday, was serious.

"He (Muhammet) is in intensive care and his treatment is continuing with him attached to respiratory equipment. I cannot say he is critical but he is serious," Huseyin Avni Sahin, chief doctor at Van hospital in eastern Turkey, told Reuters.

The four dead Turkish children are the first human bird flu fatalities outside China and Southeast Asia since the deadly virus re-emerged in late 2003.