Lukashenko's office announced the dismissal of Sergei Martynov on Monday (20 August). Martynov, 59, who had held the post since 2003, did not provide any reasons for the decision.
Lukashenko named 54-year-old Vladimir Makei, previously his chief-of-staff, as the country's new foreign minister.
Earlier this month, Belarus expelled Sweden's ambassador after a plane chartered by a Swedish public relations firm dropped about 800 toy bears over the authoritarian country in July, each carrying a message urging the former Soviet republic to show greater respect for human rights.
Lukashenko sacked two generals, including the head of air defence, and told the incoming border guards chief to use weapons if necessary to shoot down any future foreign intruders into Belarussian air space.
The move damaged already strained relations between Minsk and the EU, which has long criticised Lukashenko's policies and has imposed travel bans and asset freezes on him and other senior officials.
The EU said in a statement on Monday that Makei was one of the targeted officials.
"Mr Makei is currently subject to EU restrictive measures. In the context of the upcoming review of restrictive measures, in the autumn of this year, the EU will assess his situation," it said.
"The EU confirms its policy of critical engagement towards Belarus and reiterates its firm commitment to strengthening its engagement with the Belarussian people and civil society and to supporting the democratic aspirations of the Belarussian people."