Swiss police are pursuing four suspects believed to be associated with the Nov. 13 Paris attacks, Geneva officials said Thursday. Switzerland also raised its security level and deployed guards at the United Nations offices in Geneva.

"The Geneva police, on the basis of this information, have increased their level of vigilance and reinforced the number of police agents on the ground," the Geneva department of security said in a statement, reported.

Switzerland deployed guards with MP5 sub-machine guns at entry points to the U.N. complex in Geneva, Reuters reported. Geneva's security department said that Swiss federal authorities had flagged "suspicious individuals susceptible to being in Geneva or the Geneva region," the Associated Press reported.

Abdelhamid Abaaoud, the suspected mastermind of the Paris attacks, which claimed 130 lives, was killed five days later in a police raid in the Paris suburb of Saint-Denis. Abaaoud reportedly was implicated in four of six foiled terrorist attacks by the Islamic State group in France this year.

Other suspected terrorists believed to be linked to the Paris attacks -- that occurred at six sites around the city -- include Salah Abdeslam who is still on the run and is believed to have traveled to Greece by ferry from Italy in August. Two other suicide bombers reportedly crossed over to Leros, Greece, from Turkey in October, disguised as refugees.