"Eight days we are here in Doha and it's enough. We want to go home," Meral, 47, who lives near Dusseldorf told AFP as she and her partner Hussein, 52, wheeled their bags to a waiting private car to speed them to Saudi Arabia.

Their vessel, the Mein Schiff 5, and another, The Celestyal Journey -- two towering, multi-story cruise ships -- have been anchored at Doha's Mina port since Iran launched a retaliatory missile and drone campaign against Gulf neighbours following US-Israeli strikes.

The war has spread to the otherwise stable Gulf, shutting shipping lanes, grounding flights and unexpectedly stranding travellers, including around 15,000 cruise ship passengers in the region, according to the United Nations' migration agency.

Meral, who asked to be identified only by her first name, said passengers at the port had heard explosions overhead as Qatari air defences intercepted Iranian missiles and drones and passengers were instructed to shelter and stay far from windows.

"I was afraid... I think 99 percent of the passengers have never experienced something like this," she said.

- 'Happy to leave' -

The German national said the pair had privately arranged their own transfer for the roughly 570-kilometre overland journey to Riyadh, a lifeline for stranded tourists in Qatar where sea and air travel were suspended on February 28 and only a handful of flights have departed through a secure air corridor.

Several passengers told AFP that hundreds of people remained on the Mein Schiff 5 with a batch of 290 due to be evacuated through arrangements by German tour operator TUI for Riyadh later on Saturday.

TUI did not immediately respond to a request for comment from AFP.

As some passengers went for walks around the port or climbed into waiting vehicles later on Saturday, a government alert sounded from mobile phones warning of an elevated threat level and ordering people to take shelter.

In the city centre, past the brightly coloured buildings of the Old Doha Port tourist district, warning sirens wailed.

Later Qatar's defence ministry said the military intercepted a missile attack from Iran.

Dozens of passengers from The Celestyal Journey, some of whom said they were from central Asia, hung back in the shade of Doha's cruise ship terminal and were counted onto an idling bus that would also take them to Riyadh.

"We are happy to leave," Doniyor, 16, from Tashkent, Uzbekistan told AFP as he carried his family's bags to the bus filling with passengers.

- 'No information' -

Doniyor said his mother, grandmother and brother would travel eight hours by bus to Riyadh before catching flights, adding it was "sad" their trip had ended on such a low note.

Greece-based operator of Celestyal Journey, Celestyal Cruises also did not immediately respond to a request for comment.

Passengers said the first to be evacuated from the Mein Schiff 5 were to be families and those with medical needs.

Yacquas Daamen, 79, from Rotterdam said he expected to be waiting several more days before he could leave.

"And now we are waiting to go out but there is no information for us. We hope in the next days that we can fly back to Holland," he said.

Daamen explained how his greatest concern was for his family at home who were the most worried about him.

Hubert Sirch, 57, from Munich, said he boarded a flight from Doha following his cruise, but the flight turned back after about half an hour when the airspace was suddenly closed as the attacks began.

At the airport, he described "chaos" before returning to the ship. Sirch said before embarking on his trip he had not anticipated the dangers of a possible war with Iran.

"I didn't think about this because the government didn't make any risk announcement," he said.