Bombs have exploded at two small hotels and a gas plant in the Turkish city of Istanbul, killing two people and injuring at least nine.
Istanbul has been on high alert for months
Two men, an Iranian and a Turk, died at the Pars Hotel in the Laleli district and the injured include Chinese, Dutch, Ukrainian and Turkmen citizens.
The Pars received a warning by phone but had only 10 minutes to react.
No group has claimed responsibility for the attacks in a city where Kurdish, Islamist and leftist militants are all active.
The latest blasts appeared "to be a terrorist attack," Istanbul police
chief Celalettin Cerrah said, without giving further details.
Four simultaneous suicide bombings by Islamist militants in Istanbul last November killed more than 60 people.
The Turkish government has also been on the alert for attacks by Kurdish separatist militants, who called off a cease-fire in June.
Bombs went off at the two hotels at about 0200 local time (0000 GMT on Monday).
There were 37 guests staying at the Pars. The Laleli district is home to cheap accommodation and garment stores largely catering to East European tourists.
The second blast hit the Star Holiday Hotel, in the main tourist area Sultanahmet, where 20 guests were staying. Streets there were strewn with glass and concrete.
"There was a huge explosion and the glass started shattering," said Umut Akgul, who had been visiting a friend who works at the Star Holiday.
Mr Akgul told AP news agency he ran to the back of the hotel and started to help tourists evacuate the building after the explosion, which ripped off the exterior walls of the top two floors of the hotel.
An hour after the hotel blasts, two more bombs went off at a liquefied gas storage site in Istanbul's Esenyurt district.
They caused some damage but a small fire was quickly extinguished.