diff --git a/faker/providers/phone_number/cs_CZ/__init__.py b/faker/providers/phone_number/cs_CZ/__init__.py
index ddc13aaff2..d82ad297de 100644
--- a/faker/providers/phone_number/cs_CZ/__init__.py
+++ b/faker/providers/phone_number/cs_CZ/__init__.py
@@ -3,10 +3,34 @@
 
 class Provider(PhoneNumberProvider):
     # Phone numbers
-    # https://cs.wikipedia.org/wiki/Telefonn%C3%AD_%C4%8D%C3%ADslo
+    #   https://cs.wikipedia.org/wiki/Telefonn%C3%AD_%C4%8D%C3%ADslo
+    #   https://www.srovnejto.cz/blog/jake-jsou-telefonni-predvolby-do-zahranici/
 
     formats = (
-        # 601-608
+        # prefix 00420
+            # 601-608
+        "00420 601 ### ###",
+        "00420 602 ### ###",
+        "00420 603 ### ###",
+        "00420 604 ### ###",
+        "00420 605 ### ###",
+        "00420 606 ### ###",
+        "00420 607 ### ###",
+        "00420 608 ### ###",
+            # 702-705
+        "00420 702 ### ###",
+        "00420 703 ### ###",
+        "00420 704 ### ###",
+        "00420 705 ### ###",
+            # 720-739
+        "00420 72# ### ###",
+        "00420 73# ### ###",
+            # 770-779
+        "00420 77# ### ###",
+            # 790-799
+        "00420 79# ### ###",
+        # prefix +420
+            # 601-608
         "+420 601 ### ###",
         "+420 602 ### ###",
         "+420 603 ### ###",
@@ -15,16 +39,16 @@ class Provider(PhoneNumberProvider):
         "+420 606 ### ###",
         "+420 607 ### ###",
         "+420 608 ### ###",
-        # 702-705
+            # 702-705
         "+420 702 ### ###",
         "+420 703 ### ###",
         "+420 704 ### ###",
         "+420 705 ### ###",
-        # 720-739
+            # 720-739
         "+420 72# ### ###",
         "+420 73# ### ###",
-        # 770-779
+            # 770-779
         "+420 77# ### ###",
-        # 790-799
+            # 790-799
         "+420 79# ### ###",
     )
diff --git a/faker/providers/phone_number/sk_SK/__init__.py b/faker/providers/phone_number/sk_SK/__init__.py
index 632b186aa7..9d4cd410d8 100644
--- a/faker/providers/phone_number/sk_SK/__init__.py
+++ b/faker/providers/phone_number/sk_SK/__init__.py
@@ -3,6 +3,16 @@
 
 class Provider(PhoneNumberProvider):
     formats = (
+        "00421 2 ########",
+        "00421 3# ### ####",
+        "00421 4# ### ####",
+        "00421 5# ### ####",
+        "00421 90# ### ###",
+        "00421 91# ### ###",
+        "00421 940 ### ###",
+        "00421 944 ### ###",
+        "00421 948 ### ###",
+        "00421 949 ### ###",
         "+421 2 ########",
         "+421 3# ### ####",
         "+421 4# ### ####",
diff --git a/tests/providers/test_phone_number.py b/tests/providers/test_phone_number.py
index ff3c58abb8..bb936552ed 100644
--- a/tests/providers/test_phone_number.py
+++ b/tests/providers/test_phone_number.py
@@ -62,6 +62,25 @@ def test_phone_number(self, faker, num_samples):
             phone_number = faker.phone_number()
             assert pattern.fullmatch(phone_number)
 
+class TestCsCz:
+    """Test cs_CZ phone number provider methods"""
+
+    def test_phone_number(self, faker, num_samples):
+        pattern: Pattern = re.compile(r"^(00420|\+420)? ?[1-9][0-9]{2} ?[0-9]{3} ?[0-9]{3}$")
+        for _ in range(num_samples):
+            phone_number = faker.phone_number()
+            assert pattern.fullmatch(phone_number)
+
+            
+class TestSkSk:
+    """Test sk_SK phone number provider methods"""
+
+    def test_phone_number(self, faker, num_samples):
+        pattern: Pattern = re.compile(r"^(00421|\+421)? ?[2-9][0-9]{2} ?[0-9]{3} ?[0-9]{3}$")
+        for _ in range(num_samples):
+            phone_number = faker.phone_number()
+            assert pattern.fullmatch(phone_number)
+
 
 class TestPtBr:
     """Test pt_BR phone number provider methods"""