UNITED NATIONS, June 3 (Xinhua) -- UN Secretary-General Antonio Guterres is alarmed by the reported exchange of fire overnight between the United States and Iran and by reports that Iran has targeted Kuwait and Bahrain, his spokesperson said Wednesday.

The UN chief "is deeply troubled by reports of civilian casualties," spokesperson Stephane Dujarric told a daily briefing.

"The Secretary-General calls on all parties to exercise maximum restraint and to avoid any further escalation that risks undermining ongoing diplomatic efforts," said Dujarric, stressing that the sovereignty and territorial integrity of all countries must be fully respected.

He said the secretary-general condemns all attacks on civilian infrastructure and recalls that international humanitarian law strictly prohibits the targeting of civilian objects, and calls on all parties to uphold their obligations under international law and to take all feasible precautions to protect civilians.

"The Secretary-General reaffirms his full support for all ongoing mediation efforts, including those led by Pakistan, and urges all parties to engage constructively and in good faith with diplomatic initiatives," said the spokesperson. ■