Scores of German police raided alleged Islamist sites in Berlin early on Friday, arresting two men suspected of being part of a group planning to carry out an attack in Syria, police said.

Around 250 police officers carried out the raids on 11 sites in the German capital, arresting the two men of Turkish origin aged 41 and 43, police said in a statement.

Police on Thursday arrested a German-Tunisian man suspected of having joined the Islamic State (IS) jihadist group in Syria, the federal prosecutor's office said.

The 26-year-old suspect, named as Ayub B., is thought to have entered Syria via Turkey last year to be trained in IS combat and recruiting, before returning to Germany in August, the German prosecutor said in a statement.

German Chancellor Angela Merkel will visit Britain next week for talks with Prime Minister David Cameron, her office said Friday.

The visit Wednesday will focus on bilateral, European and international issues and on preparations for a G7 summit Germany hosts in Bavaria state on June 7-8, a statement said.

There's little to break the monotony of communist-era apartment blocks stretching across Marzahn-Hellersdorf, an east Berlin satellite district that has gained national notoriety for a spate of anti-foreigner protests.

Week after week, hundreds of residents here have angrily rallied against plans for a new center to house refugees seeking asylum on a stretch of parkland now ringed by cyclone fence and watched by security guards.

About 10,000 people had to be evacuated on Thursday after an unexploded 250-kilogram (550-pound) World War II bomb was discovered in a city near the German capital.

The find during construction work near Potsdam central railway station also halted local bus, tram and train services and led authorities to clear ministry buildings and the parliament of Brandenburg state.

Prime Minister Tammam Salam is planning to visit Brussels in December to discuss with European Union officials the burden of Syrian refugees, An Nahar daily reported on Friday.

Salam is mulling to discuss with the European officials promised assistance to Lebanon, which is hosting around 1.5 million Syrian refugees, said the newspaper.

German Foreign Minister Frank-Walter Steinmeier, fresh from a tense mission to Ukraine and Russia, said Wednesday he had not given up on a tattered truce agreement between the sides.

Steinmeier warned after talks in Berlin with his Polish counterpart Grzegorz Schetyna against calling the two-month-old ceasefire agreed in Minsk "history".

Social Affairs Minister Rashid Derbas said the number of Syrians seeking refuge in Lebanon has been dropping although a decision on not to accept more refugees hasn't been fully implemented yet.

The UNHCR reports show that the number of refugees in Lebanon began to decline, Derbas told An Nahar newspaper in remarks published on Tuesday.

German Chancellor Angela Merkel said Sunday that the fall of the Berlin Wall 25 years ago was a message to a conflict-torn world that "dreams can come true".

She spoke as Germany celebrated the milestone on November 9, 1989, that ended its Cold War division by throwing a huge open-air party at Berlin's iconic Brandenburg Gate.

Germany marks 25 years since the euphoric fall of the Berlin Wall Sunday with more than a million people expected to join tributes, festivities and an open-air party with freedom icons and rock stars.

Chancellor Angela Merkel leads commemorations for those killed trying to flee communist East Germany, ahead of a giant festival to celebrate the peaceful revolution that ended Europe's Cold War division on November 9, 1989.