Germany summoned the Iranian ambassador on Tuesday after his country briefly closed its airspace to Chancellor Angela Merkel's plane, foreign minister Guido Westerwelle said, AFP reported.
"Hindering the German chancellor's passage over Iran is absolutely unacceptable. It shows a lack of respect towards Germany that we will not accept," Westerwelle said in a statement, The Times of India reported.
"That is why I have summoned the Iranian ambassador. We shall make it very plain that such a breach of international conventions will in no way be tolerated by Germany," he added.
Iran denied Merkel's plane flyover rights while en route to India overnight, her spokesman said.
"Strange start to Indian trip -- Iran temporarily denies overflight to chancellor's plane. Delayed landing in Delhi," Steffen Seibert said in a message sent on microblogging site Twitter.
The reason for the overflight denial was not immediately known.
Media reports said the plane carrying Merkel and a high-level delegation had to circle for two hours over Turkey before receiving permission to cross Iranian airspace.
A second plane with four of Merkel's ministers and other delegation members was not delayed.