Foreign Secretary Tehmina Janjua summoned the British High Commissioner in Pakistan Thomas Drew over slogans being displayed on London taxis.
According to a statement released by the Foreign Office, "the high commissioner was informed that Pakistan, in line with the UN Charter, rejects actions and advertisements with malicious content that impinge on our sovereignty and territorial integrity."
The issue is also being raised with the Foreign and Commonwealth Office by the Pakistan High Commissioner in London, the Foreign Office said in a statement.
According to media reports, "Free Balochistan" slogans appeared on taxis in London.
In September this year, Pakistan had summoned the Swiss ambassador over the public display of anti-Pakistan posters by a group in Switzerland.
Balochistan is the largest of Pakistan's four provinces, but people in the restive region have long complained that they do not get a fair share of its natural resources.
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