Turkish Prime Minister Recep Tayyip Erdogan is in hospital after suffering a drop in blood sugar but is in a stable condition, officials say.
Mr Erdogan, 52, is a former professional football player
Foreign Minister Abdullah Gul said Mr Erdogan's sudden illness was caused by a mix of intense work and fasting for the Muslim holy month of Ramadan.
"There's no cause for alarm. Everything is under control," Mr Gul said.
Mr Erdogan had been due to address his ruling Justice and Development Party (AK). The meeting has been cancelled.
Local TV media reported that the premier was taken to hospital after he had difficulty pushing open a car door, and that his security guards had to break a window to let him out.
However, Mr Erdogan's spokesman, Akif Beki, said the prime minister had had trouble leaving the vehicle because of a problem with the door's locking system.
The 52-year-old leads an active lifestyle that includes a lot of foreign travel. In recent weeks he has visited the US, UK and Saudi Arabia.
He spent a brief time in hospital in April after suffering from a muscular spasm.