diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a6b2d9..7ce625d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to
 - build:
   - Support setuptools.packages.find.where directive in setup converter.
   - Support setuptools.data-files directives in setup converter.
+- log: Support log levels higher than INFO in `setup_logger()` (#89).
 
 ### Changed
 
diff --git a/src/log/README.md b/src/log/README.md
index fb99f81..c255a3b 100644
--- a/src/log/README.md
+++ b/src/log/README.md
@@ -1,3 +1,53 @@
 # RFL: log package
 
 Logging utility.
+
+## setup_logger()
+
+Configure the root logger with a stream handler, formatter, and per-component
+filtering.
+
+### Basic usage
+
+```python
+import logging
+from rfl.log import setup_logger
+
+setup_logger()                          # INFO level (default)
+setup_logger(debug=True)                # DEBUG level
+setup_logger(level=logging.WARNING)     # WARNING and above
+setup_logger(level="ERROR")             # string level names also accepted
+```
+
+### Log level
+
+Level is resolved in this order:
+
+1. `level` argument (int constant or string name: `DEBUG`, `INFO`, `WARNING`,
+   `ERROR`, `CRITICAL`)
+2. `debug=True` → `DEBUG` (when `level` is omitted)
+3. default → `INFO`
+
+The `debug` flag also controls formatter verbosity (detailed prefixes), independent
+of the resolved log level.
+
+### Component filtering
+
+By default, only log records from components listed in `log_flags` are shown for
+INFO and above. DEBUG records require `debug_flags`.
+
+```python
+setup_logger(log_flags=["rfl"])                    # INFO+ from rfl only
+setup_logger(debug=True, debug_flags=["network"])  # DEBUG from network only
+setup_logger(log_flags=["ALL"], debug_flags=["ALL"])  # show everything
+```
+
+Component names are derived from the first segment of the logger name
+(e.g. `rfl.pkg.module` → `rfl`).
+
+### Other options
+
+- `component`: prefix log lines with a fixed component label in the formatter
+- `formatter`: formatter class factory (default: TTY or daemon auto-selection)
+- `clear`: when `True` (default), remove existing root handlers before setup;
+  set `clear=False` to stack handlers
diff --git a/src/log/rfl/log/__init__.py b/src/log/rfl/log/__init__.py
index 9e04c96..887c15a 100644
--- a/src/log/rfl/log/__init__.py
+++ b/src/log/rfl/log/__init__.py
@@ -4,7 +4,7 @@
 #
 # SPDX-License-Identifier: LGPL-3.0-or-later
 
-from typing import Optional, List
+from typing import Optional, List, Union
 import logging
 
 from .formatters import TTYFormatter, DaemonFormatter, auto_formatter
@@ -22,18 +22,32 @@
 
 def setup_logger(
     debug: bool = False,
+    level: Optional[Union[int, str]] = None,
     log_flags: Optional[List[str]] = None,
     debug_flags: Optional[List[str]] = None,
     formatter: logging.Formatter = auto_formatter(),
     component: Optional[str] = None,
     clear: bool = True,
 ) -> None:
-    """Setup root logger debug level, debug flags and formatter.
+    """Setup root logger level, debug flags and formatter.
+
+    Log level is resolved in this order: explicit level argument, then
+    debug=True (DEBUG), otherwise INFO. The debug flag also controls
+    formatter verbosity, independent of the resolved log level.
 
     When clear is True (default), existing root logger handlers are removed
     before adding a new one, similarly to logging.basicConfig(force=True).
     """
-    if debug:
+    if level is not None:
+        if isinstance(level, str):
+            logging_level = getattr(logging, level.upper(), None)
+            if not isinstance(logging_level, int):
+                raise ValueError(f"Unknown log level: {level}")
+        elif isinstance(level, int):
+            logging_level = level
+        else:
+            raise TypeError(f"Unsupported log level type: {type(level).__name__}")
+    elif debug:
         logging_level = logging.DEBUG
     else:
         logging_level = logging.INFO
diff --git a/src/log/rfl/tests/test_setup.py b/src/log/rfl/tests/test_setup.py
index 42496e6..aa59faa 100644
--- a/src/log/rfl/tests/test_setup.py
+++ b/src/log/rfl/tests/test_setup.py
@@ -48,6 +48,42 @@ def test_setup_debug(self):
         handler = logger.handlers[-1]
         self.assertEqual(handler.level, logging.DEBUG)
 
+    def test_setup_warning(self):
+        setup_logger(level=logging.WARNING)
+        logger = logging.getLogger()
+        self.assertEqual(logger.level, logging.WARNING)
+        handler = logger.handlers[-1]
+        self.assertEqual(handler.level, logging.WARNING)
+
+    def test_setup_error(self):
+        setup_logger(level=logging.ERROR)
+        logger = logging.getLogger()
+        self.assertEqual(logger.level, logging.ERROR)
+        handler = logger.handlers[-1]
+        self.assertEqual(handler.level, logging.ERROR)
+
+    def test_setup_level_string(self):
+        setup_logger(level="WARNING")
+        logger = logging.getLogger()
+        self.assertEqual(logger.level, logging.WARNING)
+        handler = logger.handlers[-1]
+        self.assertEqual(handler.level, logging.WARNING)
+
+    def test_setup_level_overrides_debug(self):
+        setup_logger(level=logging.WARNING, debug=True)
+        logger = logging.getLogger()
+        self.assertEqual(logger.level, logging.WARNING)
+        handler = logger.handlers[-1]
+        self.assertEqual(handler.level, logging.WARNING)
+
+    def test_setup_invalid_level(self):
+        with self.assertRaisesRegex(ValueError, r"Unknown log level: NOTALEVEL"):
+            setup_logger(level="NOTALEVEL")
+
+    def test_setup_invalid_level_type(self):
+        with self.assertRaisesRegex(TypeError, r"Unsupported log level type: float"):
+            setup_logger(level=1.5)
+
     def test_setup_filter(self):
         setup_logger(log_flags=["rfl"])
         # get root logger