Merkel places white roses at attack site

German leader Angela Merkel is paying her respects at the site of a possible terror attack in Berlin.

German leader Angela Merkel has paid her respects at the site of an attack in Berlin. (AAP)

Chancellor Angela Merkel and other senior German officials have laid white roses at the site of a likely terror attack on a Christmas market in Berlin.

Merkel was joined by Interior Minister Thomas de Maiziere, Foreign Minister Frank-Walter Steinmeier and Berlin Mayor Michael Mueller at the site near the Kaiser Wilhelm Memorial Church in central Berlin on Tuesday.

They spoke with police officers at the market then signed a book of condolences at the church.

Twelve people were killed when a truck ploughed into the crowd on Monday night in what authorities are treating as a terror attack.