Thirteen Polish nationals have died and 30 others have been injured when a bus bound for Zagreb veered off a motorway in northern Croatia.
The injured were taken to hospitals in the area and 18 were in serious condition, Maja Grba Bujevi, head of Croatia's emergency services.
Sixteen emergency medical teams were dispatched to the crash site.
Polish consulate employee Dagmara Lukovic said the passengers were Polish. According to the Croatian interior ministry, the bus was registered in Poland.
The Polish prime minister, Mateusz Morawiecki, said the bus was taking pilgrims to the Catholic shrine in Medjugorje, a town in southern Bosnia.
The shrine is Europe's third most popular pilgrimage destination after Lourdes and Fatima, although the Vatican has not verified any of the reported miracles that witnesses claimed to have seen there.
I spoke about the details of the tragedy with the Croatian prime minister Andrej Plenkovi, who assured the full support of Croatian medical services, Morawiecki said on Facebook.
According to some information, the bus originated from a place near Warsaw and carried pilgrims to Medjugorje, according to the Croatian interior minister, Davor Bo inovi.
The accident occurred at 5.40 am local time, 3.40 am GMT, about 50 km 30 miles north of Zagreb, on the A 4 motorway, which is busy during the peak tourist season.
Rescue teams were sent to the location of the accident and an investigation was opened into what caused the accident, Croatian media reported.
Croatia has attracted millions of tourists this summer, with about 580,000 Polish tourists visiting between January and July.
In July last year, 10 tourists from Kosovo died in a bus crash on a highway in eastern Croatia.