ISTANBUL (AP) — Mustafa Koc, chairman of Turkey's top industrial conglomerate, Koc Holding, died from a heart attack on Thursday, a hospital said. He was 55.

The American Hospital in Istanbul said Koc died after suffering a heart attack at home. He was rushed to a state hospital near his home before being transported by helicopter to the hospital. Media reports said he was taken ill while exercising.

Koc Holding's interests range from the automotive sector to durable goods and energy. Koc had been at the head since 2003. The conglomerate employs some 100,000 people.

He took over the company from his father Rahmi Koc, the retired 84-year-old patriarch of the Koc family — one of Turkey's wealthiest.

The company was founded in 1926 in Ankara by Mustafa Koc's grandfather, Vehbi Koc, who died in 1996.

The Switzerland and U.S.-educated Mustafa Koc was Vehbi's oldest grandson. After graduation in 1984, he began working as a sales official at the conglomerate's Tofas automotive division.

Prime Minister Ahmet Davutoglu, speaking to Turkish journalists in Davos, Switzerland, described his death as a "great loss" for Turkey.

As well as his father, Mustafa Koc is survived by his wife Caroline, his two daughters and his two brothers, Omer and Ali.

The funeral was scheduled for Sunday in Istanbul.