LONDON—The U.K. government on Friday announced the new head of the U.K.’s foreign spy agency, MI6, as Alex Younger, an insider with direct experience in Afghanistan and counter terrorism who will take up his role amid increasing efforts by the U.K. and its allies to combat the threat from extremist militants Islamic State.

Before joining MI6 Alex Younger was an officer in the British army. U.K. Foreign & Commonwealth Office

Mr. Younger has been overseeing the agency’s world-wide operations, putting him second in command for operations behind the current chief Sir John Sawers. Mr. Younger has had experience of postings in Europe and the Middle East, where he was the leading officer in Afghanistan. He also led MI6’s counter terror operations in the three years leading up to the London 2012 Olympic Games. Prior to joining the agency, he was an officer in the British army.

Mr. Younger has also helped lead the agency’s modernization effort. He will take up his post next month from Mr. Sawers as Chief of the Secret Intelligence Service.

“Our dedicated staff work tirelessly against an array of threats that this country faces,” Mr. Younger said in a statement. “They do so in close partnership with both MI5 and GCHQ with whom I am looking forward to cooperating closely,” Mr. Younger added, referring to the U.K.’s domestic and communications intelligence agencies.

The announcement comes as British Prime Minister David Cameron was in Afghanistan, where he met with the new president, Ashraf Ghani. The two leaders discussed ways that they can continue to work to combat terrorism. It comes amid an escalating military effort by the U.K. and other allies to combat the militant extremist group Islamic State.

Write to Cassell Bryan-Low at cassell.bryan-low@wsj.com