(CNN) -- Germany is summoning the Iranian ambassador Monday to explain the disputed presidential election in the Middle Eastern nation, particularly the "brutal handling" of protesters, the German foreign minister said.
Supporters of defeated Iranian presidential candidate Mir Hossein Mousavi protest in Tehran on June 13, 2009.
The move is noteworthy because global reaction to the Iranian election has been guarded.
In addition, Germany is one of Iran's biggest trading partners and has taken the lead in trying to persuade it from developing a nuclear program.
"I have already prompted Iran, together with European colleagues today, to quickly shed light on what has happened there -- if one can take the announced election results there seriously or not," Foreign Minister Frank-Walter Steinmeier told German public television station ARD on Sunday.
He said the Foreign Office has asked the Iranian ambassador to Germany to explain Monday.
The Iranian government announced that President Mahmoud Ahmadinejad won Friday's election with 62.63 percent of the vote. The result sparked protests by supporters of his main rival, Mir Hossein Moussavi, who claim the vote was rigged.
U.S. Vice President Joe Biden expressed doubts Sunday about the validity of the election, but said it will take time to analyze the results.
Some other countries, such as Canada and France, also voiced concern about vote irregularities but have not explicitly refused to accept the results.
Afghanistan and Pakistan, both of which are Iran's neighbors, have officially congratulated Ahmadinejad.