António Costa, Portugal’s Prime Minister, Resigns Unexpectedly

Prime Minister António Costa of Portugal resigned unexpectedly on Tuesday, hours after the police raided government buildings as part of an inquiry into corruption and “influence peddling” and issued an arrest warrant for Mr. Costa’s chief of staff.

Mr. Costa, who had been in power since 2015, said in televised remarks that he had been “surprised” to learn that he would be the subject of criminal proceedings and that “no illicit act weighs on my conscience.”

“However, I believe that the dignity of the office of the prime minister is not compatible with any suspicion about your integrity, your good conduct and even less with the practical suspicion of any criminal act,” he added. “Therefore, in these circumstances, obviously, I presented my resignation.”

A judge authorized police to search of 37 locations — including the office of Mr. Costa’s chief of staff, the Ministry of Environment, the Ministry of Infrastructure, a City Council office in the town of Sines and several private homes, according to a statement from the prosecutor general’s office.

The investigation relates to lithium exploration concessions in northern Portugal and a hydrogen-energy production plant and data center in Sines, on the country’s southern coast, the statement said.

It did not name Mr. Costa, but said that arrest warrants were issued for the head of the prime minister’s office — identified by local media as Vítor Escária — along with the mayor of Sines and three other individuals. Portugal’s minister of infrastructure and the head of Portugal’s Environmental Agency were also named as suspects in the statement.

The prosecutor’s office said that investigation showed that the suspects had invoked Mr. Costa’s name and authority “to unblock procedures” in relation to the exploration concessions.