The move comes after 11 people including six police officers were killed on Tuesday in a car bomb attack on a police bus during morning rush hour in central Istanbul. Newspaper reports said the explosives used were fortified by fertilisers.

"As of yesterday, Turkey has banned the sale of fertilisers which could be used as explosives," Agriculture Minister Faruk Celik told state broadcaster TRT Haber, adding that 64,000 tonnes had so far been seized.

Shares in fertilizer producers dropped over three percent on the Istanbul stock exchange.

NATO member Turkey faces security threats on several fronts, including from Islamic State militants who have been blamed for two suicide bombings in Istanbul, and Kurdish militants blamed for this week's attack in the city.

Violence in the predominantly Kurdish southeast is at its worst in two decades after a ceasefire between the outlawed Kurdistan Workers Party (PKK) and the state collapsed last July. Security forces in the region have frequently been targeted by car bombs and similar attacks have hit the capital Ankara.

Celik said prior to the ban, the fertilizer with ammonium nitrate which can be used to reinforce explosives was available for sale at 9,700 locations across Turkey.

The Haberturk newspaper said the government was also planning additional measures to tighten controls on the movement of fertilisers, including installing a chip on packages and increasing audits on importer companies.

said in a statement to the stock exchange that it had suspended its fertilizer production with nitrate content. The company produced nearly half a million tonnes of chemical fertilisers in 2015, according to its annual report. BAGFAS shares were down 3 percent while shares in Gubretas , another producer, fell nearly 4.5 percent. (Reporting by Humeyra Pamuk and Seda Sezer; Editing by Nick Tattersall and Richard Balmforth)

Fertilizer producer Bandirma Gubre Fabrikalari (BAGFAS)