Germany shut down two train stations in Munich about an hour before midnight on Thursday following a tip from the intelligence service of a friendly country that the Islamic State (IS) militant group was planning a suicide bomb attack.

The action by German authorities added to jitters in many capitals as Europe ushered in the New Year with heightened security after a year of militant attacks, the biggest of which killed 130 in Paris in November.

The stations - Munich's central station and Pasing station some 8 km (5 miles) away - reopened several hours later after the tip-off could not be substantiated.

But a Munich police spokesman said on Friday: "The situation has not eased and the terror alert remains."

He declined further comment, saying a news conference would be held at 1030 GMT.

On their Twitter feed, Munich police said: "Good morning to those, who spent the night out in #munich! Thanks for staying calm and for your understanding concerning our measures."

Earlier, Bavarian Interior Minister Joachim Herrmann told a news conference that Germany had received a tip from another country's intelligence service that IS planned to attack Munich. He did not name the country but German television said in an unsourced report that the tip-off came from France.

Five to seven suicide bombers were to take part in the attack, Munich police chief Hubertus Andrae said.

"The Federal Criminal Police Office informed the Bavarian police on New Year's Eve of the existence of a tip-off from a friendly intelligence agency that Islamic State plans a concrete attack, attacks tonight, at midnight at the Munich central station or/and Pasing (station)," Herrmann told reporters.

"I believe this decision was right because I think we cannot take unnecessary risks when we are dealing with such concrete threats, concrete locations, and a concrete time," he said.

On Dec. 26, police in the Austrian capital Vienna said a "friendly" intelligence service had warned European capitals of the possibility of a shooting or bomb attack before New Year, and that police across the continent had stepped up security measures.

On Wednesday, Belgian authorities cancelled a New Year's Eve firework display, citing fears of a possible attack. Belgian police said late on Thursday three people were being held for questioning as part of an investigation into an alleged plot.

Last year was the deadliest year of militant attacks in Europe since 2004. Evidence that two of the Paris attackers had entered the continent under cover of a wave of Middle Eastern refugees heightened anxieties over the migration crisis.