Tuesday's game between Germany and the Netherlands was cancelled shortly before it was set to begin because of the serious threat of an attack at the stadium in Hanover.

A stadium announcement said the game had been cancelled as fans were arriving at HDI-Arena.

Police said they believed there was "concrete evidence" at the stadium Tuesday, four days after Germany's game against France was attacked as part of the events in Paris last week.

"A bomb attack was planned inside the stadium," Hanover police president Volker Kluwe said. "We want to avoid crowds of people, also at stations. That's why we have requested everyone go home."

Lower Saxony Interior Minister Boris Pistorius, speaking at a late news conference, said no explosives had been found by then -- despite earlier reports of police saying otherwise -- and no arrests had been made.

Pistorius said there was no confirmation of rumours that an explosive device was placed in an ambulance or another vehicle inside or outside the stadium.

Federal Interior Minister Thomas de Maiziere told the same news conference that indications of a planned attack became stronger as the match approached, and that the game was called off at his recommendation.

"We were all looking forward to the game, which was a special gesture of football and this makes it all the more bitter to have to take this decision, which was particularly hard to take, but in the slightest doubt, our priority was to protect people," De Maiziere said.

"I can understand all the questions relating to what was the background? What could have happened? Why we had to call the game off? What made the decision so clear? I can understand these questions, but please understand that I would not like to give an answer.

"Why? Because some of the answers would unsettle people, and it could make things difficult for us in future in making such decisions, be it in Hanover or elsewhere.

"I would just like to ask the German public to trust us, the Interior Ministry, that we had good reasons to make this decision, but it does not help for us to provide any further details."

De Maiziere said he could give few details because he needed to protect the source of information, and because "part of these answers would upset the population."

Most fans were still waiting outside when the order to evacuate came about an hour and a half before kickoff.

A police spokesperson told Bild: "The match has been cancelled. Spectators are being asked right now to leave the stadium quickly, but without panic."

Police look out at the HDI-Arena in Hanover after it was evacuated and Germany's game against the Netherlands was cancelled. JULIAN STRATENSCHULTE/AFP/Getty Images

A spokesperson for the German Football Association (DFB) said the organisation was unaware of the events before arriving at the site.

"Police redirected us on our way to the stadium, we are now at a safe location. We can't say more right now," Jens Grittner said, adding that the team had been taken to a safe location.

About an hour earlier, police had briefly sealed off the stadium after receiving reports of a suspicious suitcase. People were not let into the stadium about two and a half hours before kickoff.

Police then opened the doors and fans started coming in. After the cancellation announcement, the stadium was evacuated for a second time.

Referring to the first threat, Kluwe said, "After the first object turned out to be harmless, we got a tip that had to be taken seriously that an attack was being planned."

Germany's game against the Netherlands has been called off four days after Germany's game in Paris was attacked. Alexander Koerner/Getty Images

German Chancellor Angela Merkel and several cabinet ministers had been expected to attend the match. The decision to cancel was made shortly after Merkel and her ministers landed. She flew back to Berlin.

Police shut down parts of the main Hanover train station and several subway stations while searching the area around the stadium. A jazz concert at which around 900 concert-goers were expected was also cancelled.

A bomb disposal unit secured a suspicious package from a train in Hanover and the search was on for the man who left it there. A fellow passenger informed him he left something behind but he failed to react and left the train, police spokeswoman Sandra Perlebach told news agency dpa. The train had been on the way from Bremen to Oldenburg.

Acting DFB president Reinhard Rauball said: "It's a sad day for Germany and a sad day for German football. It's a shame for many football fans who were looking forward to a great game, a game which was to be played under different conditions to usual football games -- in the spirit of respect, and as a sign against violence and terrorism.

"For our team, within just four days, to have to go through such a tragic situation twice is not something I could have imagined.

"Thanks again to the security forces. I have great respect for the decision and know how hard it was to take it, but the safety of people is paramount."

Germany were playing France in a friendly during the attacks in Paris on Friday. The game was played to its conclusion after suicide bombers sought unsuccessfully to enter the Stade de France and blew themselves up outside.

On Monday, Belgian officials cancelled another friendly that was set for Tuesday, Belgium's home game against Spain in Brussels, because of security concerns.

Armed officers were on site at Wembley Stadium in London for France's game against England. The game was played without incident as England won 2-0.

Information from The Associated Press was used in this report.